【ONE·English || 翻译作业 Development: Mendel‘s Legacy to Genetics】

总言

??作业：没有严格按照语句结构进行翻译，有不规范之处。下述目录中每一小节是按照原文段落划分。
??相关链接：pubmed中查阅的链接，提供了两处文章平台。

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part1

1.1

IN 1900, Gregor Mendel’s (1866) paper was rediscovered and restored to the scientific community.

1900年，格雷戈尔·孟德尔（Gregor Mendel，1866年）的文章被重新发现，并复还于科学界。
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His work was discussed, criticized, and tested, and within the decade the new discipline of genetics had been launched, on the basis of the principles embodied in that paper.

他的作品受到了讨论、批判和检验。并基于这篇论文所阐述的规则，在这十年间开创了遗传学这门新学科。
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William Castle clearly expressed the views held in common by the early Mendelians when he wrote: “What will doubtless rank as one of the great discoveries in biology, and in the study of heredity perhaps the greatest, was made by Gregor Mendel, an Austrian monk, in the garden of his cloister, some forty years ago” (CASTLE 1903, p. 535).

威廉·卡斯尔（William Castle）清楚地表达了与早期孟德尔学派的学者们持有相同的观点，他写道：“大约四十年前，奥地利僧侣格雷戈尔·孟德尔（Gregor Mendel）在他的修道院花园里做出的这项重大发现，毫无疑问可被冠以为生物学和遗传学上最伟大的发现之一。”(CASTLE 1903, p. 535)

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1.2

In the year 2000, Mendel’s paper is still being discussed and criticized, interpreted and reinterpreted, but the harmony that had prevailed in 1900 is no longer in evidence.

2000年，孟德尔的论文仍在被人们讨论和批评、解释和重释，然而盛行于1900的融洽气氛却今非昔比。
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In the year 2000, Mendel’s position as founder of genetics is being seriously challenged. (For a comprehensive discussion of these revisionist views, see HARTL and OREL 1992.)

2000年的今天，孟德尔作为遗传学创始人的地位受到了严峻的挑战。（有关这些修正主义者的观念的综合性论述，参阅HARTL and OREL 1992。）
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The traditional story, so long cherished by students of genetics, has been relegated to the status of myth: “… a myth created by the early geneticists to reinforce the belief that the laws of inheritance are obvious to anyone who looks closely enough at the problems” (BOWLER 1989, p. 103).

遗传学学生长期以来珍视的传统故事已经沦为神话：“…这是早期遗传学家们所创造的神话，旨在加强 ‘遗传规律对于任何仔细观察问题的人来说都是显而易见的’ 这一信念。“（BOWLER 1989，第 103 页）。

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1.3

Since 1965, this wave of revisionist studies has variously represented Mendel as a Darwinian whose experiments were designed primarily to support Darwinian evolution (DE BEER 1964), as a hybridist “whose overriding concern was with the role of hybrids in the genesis of new species… The laws of inheritance were only of concern to him in so far as they bore on his analysis of the evolutionary role of hybrids” (OLBY 1979, p. 67), or as a student investigating the properties and behavior of the hybrid per se: “The real objective of the work was the creation of a mathematically precise science of hybridization modelled upon the physical sciences” (MONAGHAN and CORCOS 1990, p. 289).

自1965年以来，这股修正主义者的研究热潮把孟德尔表述为各式各样的人。或有人认为他是达尔文主义者，他的实验设计主要用于支持达尔文进化论（DE BEER 1964），或将其描述为一个杂交学家， “他首要关心的是杂交种在新物种起源中的作用……遗传规律只有在影响到他对杂交种进化作用的分析时才会引起他的关注”（OLBY 1979，第67页）。又或是将他描述为一名研究杂交体性状和表型的学者：“这项工作的真正目的是以物理学为模型，建立数学上精确的杂交科学"(MONAGHAN and CORCOS 1990, p. 289)。
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Although these interpretations differ from each other, they agree on one point—Mendel’s principal interest was not the study of heredity.

尽管这些解释各不相同，但有一点是一致的——孟德尔的主要兴趣并不是研究遗传。
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part2：Entwicklung and development

2.1

Entwicklung and development:
When I began to study Mendel’s paper, I had no grandiose intention of flying to the defense of Mendel’s reputation.Nor was I feeling especially resentful of the revisionist views.

遗传和发育：当我开始研究孟德尔的论文时，我并没有为孟德尔的声誉辩护的宏伟意图。对于修正主义者的观点我也没有感到特别愤恨。
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After all, the subject of Mendel is still sufficiently rich to accommodate all kinds of new and differing positions.

毕竟，孟德尔的研究课题仍然十分丰富，足以容纳各种不同的立场观点。
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However, instead of rehashing the material from the translations of Mendel’s already heavily plundered work, I decided to return to the original text of Mendel’s Versucheüber Pflanzen-Hybriden.

不过，与其重新翻阅孟德尔早已被严重翻版的译文材料，我决定回归于孟德尔的《植物杂交研究》原文。
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Here I discovered a new Mendel—a Mendel who did not fit any of the revisionist pictures, but neither was he quite the hero of the traditional account.

在这里，我对孟德尔有了全新的认识——他既不符合修正主义者们所描绘的任何形象，也不属于传统观念中所认为的俊杰。
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This was a Mendel who had stepped from the pages of another story altogether—a different Mendel, who spoke of a different theme. The theme was Entwicklung, which translates into English as development.

这是一个从其它报道传说中脱颖而出的孟德尔——一个迥然不同的孟德尔，他讲述了一个独特的主题。这个主题就是 “Entwicklung”，翻译成英文就是 “发育”。
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The term Entwicklung appears in the first paragraph of the first page of Mendel’s paper and emerges and re-emerges throughout the remaining forty-odd pages with persistent regularity.

“Entwicklung”一词出现在孟德尔论文中的第一页的第一段，并在此后四十多页的文章中屡见不鲜。
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It occurs as an independent noun (always capitalized, always imposing) and frequently as an element in a compound word—e.g., die Entwicklungsreihe, developmental series; die Entwicklungsgeschichte, the history of development; das Entwicklungs-Gesetz, the law of development.

它作为一个独立的名词出现（总是大写，总是有气势），也经常作为复合词中的组成成分使用——例如，die Entwicklungsreihe，发展/发育系列；die Entwicklungsgeschichte，发展/发育史；das Entwicklungs-Gesetz，发展/发育法。

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2.2

In whatever form it occurs, however, the cumulative effect of repeated exposure to Entwicklung, in simple or compound form, is undeniable.

然而，无论以何种形式出现，以简单或复杂的组成反复出现的“Entwicklung”一词所产生的累积效应都是不可否认的。
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Entwicklung is recognizably the single most important element in Mendel’s thoughts. Its English equivalent does not fare as well.

“Entwicklung”显然是孟德尔思想中最重要的一个元素。与之相对应的英文释义就没那么匹配。
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As I recall from my own experience, as often as I had read Mendel in translation, the word development remained an unremarkable term. It was noticed and then dismissed, with little to recommend it as something significant.

据个人经验，在我常阅读的孟德尔译文中，“发育（development）”仍是一个毫不起眼的词汇。它被注意到，然后被摒弃，没有什么值得介绍的意义。
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(Incidentally, there are two translations of Mendel’s paper. The first translation appeared in 1902 in William Bateson’s Mendel’s Principles of Heredity: A Defence; the second was published in 1966 in STERN and SHERWOOD’S The Origin of Genetics—A Mendel Source Book.)

(顺便一提，孟德尔的论文有两个译本。第一个译本出现于 1902 年，William Bateson 的《孟德尔遗传原理：辩护》中；第二个译本发表于1966 年， STERN 和 SHERWOOD 的《遗传学的起源——孟德尔资料集》）。

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2.3

Perhaps this reaction to development is prompted in part by the way it is treated in the translations.

也许，对“发育（development）”一词的这种反应一定程度是由译文中的处理方式引起的。
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For example, there are many instances in which Entwicklung appears in the German text, but development is omitted from the translation. It is just possible that the frequency of repetition of the term is needed to make an impression on the reader.

例如，德语文本中多次出现“ Entwicklung”，但译文中却对“development”进行了省略。这可能是为了给读者留下深刻印象，需要频繁重复该词。
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Also, in the Stern translation, the phrase the developmental series is introduced just once. The reader is then notified in a footnote (p. 2) that thereafter the phrase is replaced by the word series, even though Mendel only and always uses the phrase the developmental series.

此外，在斯特恩的译文中，“发育系列（developmental series ）”这一短语仅出现了一次。尽管孟德尔始终只使用“发育系列（developmental series）”，但译文在脚注（第 2 页）中告知读者，此后该短语将被“系列（series）”一词取代。
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Obviously, in the judgment of the translator, development has become an expendable modifier.

显然，在译者看来，“发育（development）”已成为一个可有可无的修饰词。
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And in the Bateson translation there is a seemingly minor error, but its repercussions are major.

此外，在贝特森的译本中，还有一个看似微小但实则影响重大的错误。
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Instead of stating that the purpose of Mendel’s experiments was to follow the development of the hybrids in their progeny, the translation reads: “The object was to follow up developments of the hybrids in their progeny” (p. 40).

译文没有说明孟德尔实验的目的是跟踪杂交后代的发育情况，而是写道：“follow up developments of the hybrids in their progeny”（第 40 页）。
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The simple addition of an “s” transforms Mendel’s technical term development into a nonscientific word that, in the vernacular, can be interpreted as an “event,” an “occurrence,” or a “happening,” thereby diverting attention from Mendel’s original focus on development as a biological process.

简单地加上一个 “s”，孟德尔的专业术语 "发育 "就变成了一个非科学词汇，通俗来讲可以解释为 “事件”、"发生 "或 “发生”，从而转移了人们对孟德尔最初将发育作为生物过程的关注。

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2.4

There might also have been a far more powerful, silent factor at work. Development may have become the victim of change—the change in meaning that so often occurs in the life of a word. Development in nineteenth century biology embraced both heredity and embryological change.

可能还有一个更强大、更无声的因素在起作用。 “发育” 可能是 “变化” 的牺牲品—— “变化” 的含义经常发生在一个词的生命中。“发育” 在十九世纪生物学中既包括遗传，也包括胚胎变化。
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By the time Mendel’s paper had been rediscovered and translated, development had taken on a very specialized significance in biology. It referred almost exclusively to ontogenetic change.

在孟德尔的论文被重新发现和翻译的时期，“ 发育 ”在生物学中已经具有了非常特殊的意义。它几乎完全是指个体发育变异。
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But Mendel does not discuss ontogenetic change. Thus an unusual situation arises. The word development is unaccompanied by the appropriate and expected underlying process.

但孟德尔并没有讨论个体发育变化。因此一种不寻常的情况出现了。“ 发育 ”一词没有适当的、预期的基本过程。
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In these circumstances, development could easily be glossed over, and since it now lacked biological significance, it would be dismissed as irrelevant and unimportant.

在这种情况下，“发育 ”一词很容易被忽视，因其缺乏现有的生物学意义，因此会被视为无关紧要。

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2.5

Whatever the reason for its neglect, there is no denying that the twentieth century audience has been unresponsive to Mendel’s development. How else can one explain the following anomaly?

无论忽视它的原因是什么，不可否认的是，二十世纪的读者仍然对孟德尔的“ 发育” 毫无反应。否则，如何解释以下的反常现象呢？
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Mendel is described as expressing an interest in evolution, yet the term evolution occurs only twice in his paper.

孟德尔被认为对进化论持有兴趣，但“进化（evolution）”一词在他的论文中只出现了两次。
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It is suggested that Mendel is really interested in examining the process of hybridization, but the term hybridization appears only once.

有人认为孟德尔真正感兴趣的是研究杂交过程，但“杂交（hybridization）”一词只出现了一次。
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And then, of course, there is the traditional story—that Mendel’s interest resides in the study of heredity; however, the word heredity does not appear at all.

当然，还有一种传统的说法——孟德尔的兴趣在于研究遗传，但“遗传”一词根本没有出现。
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On the other hand, although development occurs on practically every page of the paper, no one has ventured to claim that Mendel was motivated by an interest in development.

另一方面，尽管“发育”几乎出现在文章中的每一页，但没有人敢说孟德尔的动机是对发育感兴趣。

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2.6

So if Mendel is not discussing embryological development, but he regularly refers to development, what is he talking about? What is Mendelian development?

所以，若孟德尔不是在讨论胚胎发育，却又经常提到“发育”，那么他在谈论什么呢？什么是孟德尔的“发育”？

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part3：Development—a world view

3.1

Development—a world view:
That Mendel would be interested in development is neither implausible nor idiosyncratic. The concept of development, which had been relatively quiescent in the seventeenth and eighteenth centuries, had a dramatic renaissance in the nineteenth century.

孟德尔对发育持有感兴，既非难以置信，也非特立独行。在十七和十八世纪相对沉寂的“发展（development）”这一概念，在十九世纪迎来了戏剧性的复兴。
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In place of the static view of the world that had prevailed, one was now encouraged to think “developmentally”—to see things in terms of their origins and the orderly, irreversible changes that followed.

人们摒弃了以往盛行的静态世界观，转而鼓励 "发展变化"的思维——从事物的起源以及随之而来的有序、不可逆转的变化来看待事物。
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All things were governed by development, a process of unfolding, whether they were animate or inanimate, natural or humanmade. The questions that underlay nineteenth century investigation (scientific and otherwise) was: “How have things come to be what they are? What is their history?” (MERZ 1904, p. 280).

万事万物都受发展的支配，这是一个变化的过程，无论它们是有生命的还是无生命的，是自然的还是人为的。十九世纪研究（科学研究和其他研究）的基础问题是：“事物是如何形成现在这样的？它们的历史是怎样的？”(MERZ 1904 年，第 280 页）。
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3.2

One of the earliest applications of the principle of development was LaPlace’s Nebular Hypothesis of 1796 (BRUSH 1987, p. 250)—a bold attempt to explain the origin and subsequent unfolding of the solar system by natural means.

发展（development）这一理念最早的应用之一是拉普拉斯 1796 年提出的星云假说（BRUSH 1987，第 250 页）——是一个通过自然科学对太阳系的起源及随后变化进行解释的大胆尝试。
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His approach “powerfully influenced the minds of many students of nature in the direction of a genetic view of phenomena” (MERZ 1904, p. 285). In 1825, K. E. von Baer published Uber Entwickelungsgeschichte der Thiere (OSPOVAT 1976)—a history of the development of animal life, describing the changes from the simple homogeneous germ to the specialized, complex heterogeneous form.

他的研究方法 “有力地影响了许多以遗传现象为研究导向的自然学科学生们的思想”（MERZ，1904 年，第 285 页）。1825 年，冯?贝尔（K. E. von Baer） 出版了《动物个体发育（Uber Entwickelungsgeschichte der Thiere）》（OSPOVAT 1976）——这是一部动物生命发展史，描述了从简单的同质生殖到特化的复杂异质形态的变化。
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It was the Law of Development at work. And what was undeniably the grandest attempt to unify all phenomena under the principle of development came from the pen of Herbert SPENCER (1904):

这是发展规律在起作用。赫伯特·斯宾塞（Herbert Spencer）笔下的著作（1904 年）无疑是最伟大的将所有遵循发展规律的现象统一起来的尝试：
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Abundant proof has been given that the law of organic development, formulated by von Baer, is the law of all development. The advance from the simple to the complex, through a process of successive differentiations, is seen alike in the earliest changes of the Universe to which we can reason our way back and in the earliest changes that we can inductively establish; it is seen in the geologic and climatic evolution of the Earth; it is seen in the unfolding of every single organism on its surface and in the multiplication of kinds of organisms; it is seen in the evolution of Humanity, whether contemplated in the civilized individual or in the aggregate of races; it is seen in the evolution of Society in respect alike of its political, its religious, and its economical organization; and it is seen in the evolution of all those endless concrete and abstract products of human activity that constitute the environment of our daily life.

大量事实证明，冯·贝尔提出的胚胎发育规律是一切生物发生的规律。通过连续分化的过程，从简单到复杂的进化在宇宙早期就已经随处可见，根据此，我们可以推演早期个体发育的过程，并重演构建祖先的主要进化路程。这种由简到繁的过程也体现在地球地质和气候演变中；体现在地表上任何单一生物体及其种族繁衍中；体现在人类的进化过程中，无论是文明个体还是种族群体；体现在社会的进化过程中，无论是政治组织、宗教组织还是经济组织；它体现在那些构成当今日常生活环境的所有无穷无尽或具体或抽象的人类活动产物的发展过程中。
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3.4

This, then, is the panoramic view of development.

这就是发展的全景。
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It is likely that anyone preparing to investigate any area of the sciences or philosophy, society, language, or religion would have approached his or her subject developmentally.

任何准备研究科学、哲学、社会学、语言学或宗教学等任何领域的人，都可能会从发展的角度来研究他或她的课题。
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It is not too difficult to accept that Mendel would also have been so influenced. However, it is possible to locate Mendel even more precisely within the framework of development.

这就不难接受孟德尔也会受到这样的影响。然而，在发展的框架内更准确地定位孟德尔是可能的。
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3.5

First, recall that Mendel was not only a breeder and hybridist, he was a botanist; and as a botanist he would have been familiar with the textbook written by the leading botanist of the period, M. J. Schleiden (see LORCH 1969, p. xxv).

首先，孟德尔不仅是一位育种家和杂交学家，还是一位植物学家；作为一名植物学家，他对当时顶尖的植物学家施莱登（M. J. Schleiden）编写的教科书很熟悉（见 LORCH 1969, 第 xxv 页）。
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Schleiden had galvanized botany with his “hands-on, how-to” book, The Principles of Scientific Botany (1849)—and indeed, a well-thumbed copy of the third edition of The Principles was found in Mendel’s private collection (ILTIS 1932, p. 104).

施莱登的这本 "手把手教你怎么做 "的《科学植物学原理》（The Principles of Scientific Botany，1849 年）使植物学大放异彩——事实上，在孟德尔的私人收藏中还发现了一本拇指粗的第三版《原理》（ILTIS，1932 年，第 104 页）。
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Its influence was widespread; its message clear and incisive: “the one and only way to achieve scientific insight, and consequently the sole and indispensable methodological procedure which derives from the very nature of the subject, is the study of development.”

该书影响广泛；所传达的信息清晰而深刻："要想实现科学见解，并从学科本质中收获到不可或缺的单一方法论，唯一途径就是对发展的研究。
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Now, in urging the study of development, Schleiden was referring not only to the cells of the developing embryo, but also to any changes in the adult body.

现如今，在对发育的研究推进中，施莱登关注的不仅是发育中的胚胎细胞，还包括成年个体的任何变化。
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Unlike the French and English usage, which did restrict development to its narrow scope, a focus on the embryonic cells, the German Entwicklung embraced the study of change in the structure, growth, and division of embryonic and adult cells (MERZ 1904, p. 197).

法文和英文的用法将 "发育（development） "限制在狭义的范围内，即局限于胚胎细胞，而德文的 "发育（Entwicklung） "则不同，它包含了对胚胎细胞和成体细胞的结构、生长和分裂变化的研究（MERZ 1904，第 197 页）。
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Schleiden enjoined botanists to study the ordinary cells that complete their cycle of development on their own and those special cells, the germ cells, whose further development was suspended until their union in fertilization.

施莱登要求植物学家研究那些自身已经完成生长周期的普通细胞，和那些在受精结合之前被停止生长发育的特殊生殖细胞。
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Now, into this swirl of developmental activity came Mendel, who combined an interest in development and an interest in the germ cells. He had a decidedly unique view of development and a decidedly bold view of the role of the germ cell in that development.

现在，孟德尔来到了这个发育研究的漩涡中，他把对发育的兴趣和对生殖细胞的兴趣两者结合在一起。他对发育有独特的见解，对生殖细胞在发育中的作用也有大胆的看法。

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part4：Mendel on development

4.1

Mendel on development:
[All quotations from Mendel, in this section, are taken from the STERN and SHERWOOD (1966) translation.]

孟德尔论发育： [本节中所有孟德尔的引文均来自 STERN 和 SHERWOOD（1966 年）的译文]。
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Mendel introduces development to us in the very first paragraph of the first page of his paper. He informs us that he had previously carried out hybridization experiments designed to produce new color variants in ornamental plants.

孟德尔在论文第一页的第一段向我们介绍了发育。他告诉我们，他以前曾进行过杂交实验，目的是在观赏植物中产生新的颜色变体。
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The crosses had revealed a striking fact: the offspring of the hybrid forms regularly produced the same classes of progeny.

这项杂交实验揭示了一个惊人的事实：杂交后代经常产生同类型的后代。
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It was this regularity that prompted him to undertake this series of experiments “to follow the development of the hybrids in their progeny” (p. 1).

正是这种规律性促使他进行了这一系列实验，“跟踪杂交后代的发育”（第 1 页）。
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Mendel has just provided us with the first clue—development is an intergenerational process. It is begun in the hybrid parent but achieves completion in the progeny.

孟德尔为我们提供了第一条线索——发育是一个世代相传的过程。它始于杂交亲本，但在后代中完成。
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4.2

Mendel then informs us that the hybridization experiments undertaken by others have not produced the information needed to deduce “a generally applicable law of the formation and development of hybrids” (p. 2). His first set of experiments is intended to do precisely that—to give Mendel the data necessary to formulate a law of development.

随后，孟德尔告诉我们，其他人进行的杂交实验并没有获得"适用于杂交种形成和发育的普遍规律"（第 2 页）所需的信息。他的第一组实验正是为了精确地做到这一点——为他提供形成发育规律的必要数据。
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His classic artificial fertilization crosses between varieties bearing contrasting characters (yellow vs. green albumen, tall vs. short stems, etc.) are carried out, and the resulting monohybrid plants are allowed to self-fertilize.

他在具有对比特征的品种（黄蛋白与绿蛋白、高茎与矮茎等）之间进行了经典的人工受精杂交，并让产生的单交种植物进行自交。
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Each hybrid gives the same results: “Of the seeds formed by the hybrids with one pair of differing traits, one half again develop the hybrid form, while the other half yield plants that remain constant and receive the dominating and the recessive character in equal shares” (p. 15). Mendel refers to this descriptive statement as the Law of Development. By denoting the dominant constant trait by A, the recessive trait by a, and the hybrid trait by Aa, Mendel gives form to the Law of Development. It is A + 2Aa + a, and he calls this expression the developmental series (p. 16).

每个杂交种的结果都是一样的： “具有一对不同性状的杂交种所结出的种子中，有一半会再次发育形成杂交种，而另一半产生的植株则保持不变，收获到等量的显性性状和隐性性状”（第 15 页）。孟德尔将这一描述性陈述称为发育定律。他用 A 表示显性性状，用 a 表示隐性性状，用 Aa 表示杂交性状，以此表征发育定律。即， A + 2Aa + a，他称这种表达方式为发育系列（第 16 页）。
PS：“孟德尔第一定律”（即遗传分离规律）。
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4.3

These are the three facets of development that become the subject of Mendel’s inquiry: the development of the hybrid, the Law of Development, and the developmental series. And now Mendel makes a thoroughly unexpected statement: he will undertake “further experiments whose outcome would throw light on the composition of the seed and pollen cells in the hybrid” (p. 23).

这就是孟德尔探究的发育的三个方面：杂交种的发育、发育定律和发育系列。现在，孟德尔做出了一个完全出乎意料的声明：他将进行 “进一步的实验，其结果将揭示杂交种中种子和花粉细胞的组成”（第 23 页）。
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But why bring in the germ cells? What is the connection between the composition of the germ cells and development? Mendel tells us directly that the composition of the germ cells provides “an adequate explanation for the difference of forms among the progeny of hybrids as well as the ratios in which they are observed” (p. 29); i.e., the composition of the germ cells explains the production of the development series.

但是，为什么要引入生殖细胞呢？生殖细胞的组成与发育之间有什么联系？孟德尔直接告诉我们，生殖细胞的组成 “充分解释了杂交后代的形态差异以及它们之间的比例”（第 29 页）；也就是说，生殖细胞的组成解释了发育系列的产生。
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4.4

But how does one go about determining the composition of the germ cells at a time when cytologists had barely begun venturing into the nucleus? The task seems daunting at first, if not impossible. Mendel, however, succeeds in what can be described only as a brilliant tour de force. He makes use of one important clue:

但是，在细胞学专家刚刚开始涉足细胞核的时候，如何确定生殖细胞的组成呢？纵非绝无可能，但这项任务起初也是艰巨的。然而孟德尔却成功了，他的成功只能用 "神来之笔 "来形容。他利用了一条重要线索：
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… in Pisum constant forms appear among the progeny of hybrids and that they do so in all combinations of the associated traits. In our experience we find everywhere confirmation that constant progeny can be formed only when germinal cells and fertilizing pollen are alike (p. 24).

…在双子叶植物中，杂交后代中会出现恒定的形式，并且它们在相关性状的所有组合中都是如此。根据我们的经验，我们发现只有当生殖细胞和受精花粉性状相同时，才能形成稳定的后代（第 24 页）。

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4.5

Thus, if constant progeny can be formed only when the egg and pollen cells are identical, then the composition of the egg and pollen cells can be determined by merely observing the constant classes produced by the hybrid.

因此，若只有在卵细胞和花粉细胞相同的情况下才能形成性状恒定的后代，那么只需观察杂交种产生的恒定类别，就能确定卵细胞和花粉细胞的组成。
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Thus, for example, the dihybrid AaBb produces constant progeny of the forms AB, Ab, aB, and ab. Therefore, the composition of the germ cells must also be AB, Ab, aB, ab. Thus, Mendel realizes that the germ cells carry all possible combinations of a’s and b’s, but A and a or B and b never occur in the same germ cells.

例如，双因子杂交种 AaBb 产生的恒定后代性状为 AB、Ab、aB 和 ab。因此，生殖细胞的组成也必须是 AB、Ab、aB、ab。由此，孟德尔意识到生殖细胞携带着所有可能的 a/A 和 b/B 的组合，但 Aa 或 Bb 从未出现在同一个生殖细胞中。
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This is the substance of Mendel’s hypothesis—that the germ cells carry only constant combinations of traits. Mendel proceeds to confirm this hypothesis experimentally, and in an appropriate italicized fanfare he makes the following general statement:

这就是孟德尔假说的实质——生殖细胞只携带恒定的性状组合。孟德尔接着用实验证实了这一假说，并用适当的斜体大张旗鼓地做了如下一般性陈述：
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[P]ea hybrids form germinal and pollen cells that in their composition correspond in equal numbers to all the constant forms resulting from the combination of traits united through fertilization (p. 29).

杂交种形成的生殖细胞和花粉细胞，其组成与通过受精结合所产生的性状在数量上相等（第 29 页）。
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Hartl and Orel (1992) rightly describe this achievement as “the keypoint of Mendel’s discovery.” It is also the key to defining Mendelian development.

HARTL 和 OREL（1992 年）将这一成就正确地描述为 “孟德尔发现的关键点”。这也是定义孟德尔发育学的关键。

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4.6

Mendel’s first step is to demonstrate how the germ cell “explains” the production of the developmental series. He starts with the simplest case—a hybrid that bears the single hybrid trait—Aa.

孟德尔的第一步是证明生殖细胞如何“解释”发育系列的产生。他从最简单的例子开始——一个具有单一杂交性状的杂交种——Aa。
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According to his hypothesis, such a hybrid should produce equal numbers of only two kinds of germ cells: A and a. Because, in the simplest case, only four individuals are produced, this means that the hybrid forms four pollen cells and four germinal (egg) cells, described by Mendel as (p. 29):

根据他的假设，这样的杂交种只产生两种相等数量的生殖细胞：A和a。因为在这种最简单的情况下，只会产生四个个体，即杂交种形成四个花粉细胞和四个生殖（卵）细胞，孟德尔描述为（第29页）：
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$$Pollencells：A+A+a+a$$
$$Germinalcells：A+A+a+a$$

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4.7

These germ cells then participate in fertilization, but:

然后，这些生殖细胞参与受精，但是：
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[I]t is entirely a matter of chance which of the two kinds of pollen combines with each single germinal cell. However, according to the laws of probability, in an average of many cases it will always happen that every pollen form A and a will unite equally often with every germinal cell form A and a;

这两种花粉会与哪一个生殖细胞结合完全是一个随机事件。而根据概率定律，在许多情况下，平均而言每种性状为 A 和 a 的花粉细胞与每种形性状为 A 和 a 的生殖细胞结合的次数总是相同的；
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therefore, in fertilization, one of the two pollen cells A will meet a germinal cell A, the other a germinal cell a, and equally, one pollen cell a will become associated with a germinal cell A, the other with a (p. 30).

因此，在受精过程中，性状为A的花粉细胞其中一个会与性状为A的生殖细胞结合，另一个与性状为a的生殖细胞结合；同样，性状为a的花粉细胞其中一个会与性状为A的生殖细胞结合，或与生殖细胞结合（第 30 页）。
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Mendel diagrams this chance fertilization as:

孟德尔将这种随机的受精过程绘制成下图：

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He then visualizes each fertilization in the form of a fraction, in which the pollen cell occupies the numerator and the germinal cell occupies the denominator:

然后，他以分数的形式将每次受精过程形象化，其中花粉细胞占分子，生殖细胞占分母：
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$$A/A+A/a+a/A+a/a$$

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4.8

Finally, Mendel translates these fertilization fractions into the resultant classes of progeny:

最后，孟德尔将这些公式转化为杂交子代的类别：
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In the first and fourth terms germinal and pollen cells are alike; therefore the products of their association must be constant, namely A and a; in the second and third, however, a union of the two differing parental traits takes place again, therefore the forms arising from such fertilizations are absolutely identical with the hybrid from which they derive. Thus, repeated hybridization takes place (p. 30).

在第一项和第四项中，生殖细胞和花粉细胞性状相同；因此，它们结合的后代性状必然不变，即 A 和 a；然而，在第二项和第三项中，两个性状不同的亲本再次结合，因此这种受精产生的后代的性状与它们产生的杂交体完全相同。即，发生了重复杂交（第 30 页）。
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Therefore, the fertilization fractions are (p. 30)

因此，杂交公式为（第 30 页）：
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4.9

These fertilization fractions are none other than the terms of the developmental series.
The mono-, di-, and trihybrids behave in the same way, passing through these four steps to produce their characteristic developmental series:

这些杂交公式就是发育系列的术语。
单杂交种、双杂交种和三杂交种的行为也遵从上述方式，都是通过这四个步骤来产生其特有的发育系列：
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• 1、Fertilization brings together pairs of contrasting traits to form the hybrid trait;
• 2、germ cells that carry only constant combinations of traits, in equal number, are then formed;
• 3、the germ cells unite randomly in fertilization;
• 4、the different classes of progeny make their appearance.

1、受精将一对性状截然不同的物种结合在一起，形成杂种性状；
2、然后，形成只携带相同数量的恒定性状组合的生殖细胞；
3、生殖细胞在受精过程中随机结合；
4、不同表现型的子代出现。

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4.10

These are the steps that demonstrate the role of the germ cells in the production of the developmental series. But does this get us any closer to defining the development of the hybrid?

这些步骤证明了生殖细胞在发育系列中的作用。但是，这是否能让我们更接近于确定杂交种的发育过程？
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Mendel kindly comes to our aid once again. He informs us that the development of the hybrid also results in the developmental series. One may logically assume that there is only one set of steps in the formation of the developmental series.

孟德尔再次向我们伸出了援助之手。他告诉我们，杂交种的发育也会产生发育系列。我们可以合乎逻辑地假设，发育系列的形成只有一套步骤。
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Since Mendel has already elaborated the four steps that result in the developmental series, and since development of the hybrid also produces the development series (p. 21), we may conclude that those same four steps comprise the development of the hybrid. This process, which originates in the hybrid and finds completion in the progeny, is Mendelian development.

既然孟德尔已经阐述了形成遗传定律的四个步骤，而且杂交种的遗传也会生成遗传组合（第 21 页），那么我们可以得出结论，杂交种的遗传也是由这四个步骤组成的。这一过程起源于杂交种，并在后代中完成的过程，就是孟德尔的发育学（遗传学）。
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4.11

Interestingly, a letter from Mendel to Karl Nageli, dated April 18, 1867 (STERN and SHERWOOD 1966, p. 62), provides independent corroboration that Mendel viewed development as a process linking the hybrid with the different kinds of progeny it produced. In the letter, Mendel tried to convince Nageli (a believer in blending inheritance) that from a hybrid Aa one could retrieve the parental traits A and a among the progeny of that hybrid:

有趣的是，孟德尔在 1867 年 4 月 18 日写给卡尔·纳格利（Karl Nageli）的一封信（STERN and SHERWOOD 1966, p.62）中提供了一个独立的佐证，即孟德尔认为遗传是一个将杂种与其产生的不同后代联系起来的过程。在信中，孟德尔试图说服纳格利（混合遗传的信奉者），从杂交种 Aa 的后代中，可以找回亲本性状 A 和 a：
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I am inclined to regard the separation of parental traits in the progeny of hybrids in Pisum as complete and thus permanent. The progeny of hybrids carries one or the other of the parental traits, or the hybrid form of the two; I have never observed gradual transitions between the parental traits or a progressive approach towards one of them. The course of development (italics mine) consists simply in this; that in each generation the two parental traits appear, separated and unchanged, and there is nothing to indicate that one of them has either inherited or taken over anything from the other (STERN and SHERWOOD 1966, p. 62).

我倾向于认为双子叶植物杂交后代中亲本性状的分离是彻底的，也是永久的。杂交后代带有一种或另一种亲本的性状特征，或者是两者性状的混合；我从未观察到亲本性状之间逐渐过渡，或向其中一种性状逐渐靠近。遗传的过程简单地说就是：在每一代中，两个亲本性状都是分离、不变的出现的，没有任何迹象表明其中一个亲本性状继承或接管了另一个亲本性状的任何特征（STERN 和 SHERWOOD，1966 年，第 62 页）。

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4.12

But what exactly is happening in the course of Mendelian development? Mendel is describing the manner in which the hybrid trait is passed to and distributed among the progeny of the hybrid. The hybrid Aa produces progeny that are constant A, constant a, and hybrid Aa once again, in the ratio 1:1:2 (the law of development).

但孟德尔发育过程中究竟发生了什么呢？孟德尔描述了杂种性状在杂种后代中的传递和分布方式。杂交种 Aa 产生的后代是纯合子AA、aa 和杂合子Aa，比例为 1:1:2（遗传定律）。
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Moreover, without recourse to the term heredity, which was not in common use in the nineteenth century, Mendel makes it very plain that heredity is the focus of his interest:

此外，孟德尔没有使用“遗传（heredity）”这个在 19 世纪还不常用的术语，但他非常清楚地表明“遗传”是他关注的焦点：
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When two plants, constantly different in one or several traits, are crossed, the traits they have in common are transmitted unchanged to the hybrids and their progeny … a pair of differing traits, on the other hand, are united in the hybrid to form a new trait, which usually is subject to changes in the hybrid’s progeny. It was the purpose of the experiment to observe these changes for each pair of differing traits, and to deduce the law according to which they appear in successive generations (p. 5).

当一种或几种性状不同的两个植物杂交时，它们的共同性状会原封不动地传给杂交种及其后代…另一方面，一对不同的性状在杂交种中结合成一种新的性状，而这种新的性状通常会在杂种后代中发生变化。实验的目的是观察每一对不同性状的变化，并推断出它们在连续几代中出现的规律（第 5 页）。
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4.13

KING and STANFIELD’S A Dictionary of Genetics (1997, p. 157) defines heredity as a “familial phenomenon wherein biological traits appear to be transmitted from one generation to another.”

金和斯坦菲尔德的《遗传学词典》（1997 年，第 157 页）将遗传定义为 “生物特征似乎是代代相传的一种家族现象”。
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The equivalence between this definition of heredity and Mendel’s description of the “course of development” is strikingly apparent. There is no doubt that in his study of the development of the hybrid, Mendel is actively, knowingly, intentionally, dealing with heredity.

这一遗传学定义与孟德尔对 "发育过程 "的描述之间的等同性非常明显。毫无疑问，孟德尔在研究杂交种的发育过程，是积极、知情、有意识地在处理遗传问题。
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However, in concluding that Mendelian development is a study in the transmission of traits, have we not returned full circle to the traditional story? Or have we?

然而，在得出“孟德尔的发育是对性状传递的研究”这一结论时，我们是否又回到了传统故事的原点？

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4.14

Mendel is traditionally personified as the nineteenth century monk who was definitely ahead of his time. Part of his success is attributed to his very modern attitude towards heredity and development.

孟德尔历来被视为十九世纪时期走在时代前列的修道士。他的成功一部分归功于他对遗传和发育所持有的前卫态度。
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Whereas his contemporaries maintained that heredity was merely a stage in the seamless process of development, Mendel, it is claimed, recognized that the events of transmission could be detached from development and studied separately (SANDLER and SANDLER 1985).

与他同时代的人认为遗传只是持续发育过程中的一个阶段，而孟德尔则认为，遗传事件可以从发育中分离出来，单独进行研究（SANDLER 和 SANDLER，1985 年）。
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However, if we keep in mind that Mendel described his work in transmission as a study in the development of the hybrid, he suddenly does not seem to be quite so detached from his nineteenth century intellectual heritage. There is no doubt that Mendel’s focus is on the events of transmission, but he continues to think and speak and write about transmission in terms of nineteenth century development.

然而，若我们记得孟德尔把他在遗传方面的工作描述为对杂交种发育的研究，那他似乎看起来不再那么脱离19 世纪的思想遗产了。毫无疑问，孟德尔的研究重点是遗传事件，但他仍然从十九世纪的发展角度来思考、谈论和书写遗传问题。
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However, the nineteenth century garb cannot disguise his actual achievement. Mendel’s intention—“to follow the development of hybrids in their progeny”—is a step-by-step description of the transmission and distribution of hybrid traits between parent and progeny. Is it not fitting that we restore to Mendel his well-deserved title—Father of Genetics?

然而，十九世纪的包装无法掩盖他的实际成就。孟德尔的意图——“跟踪杂交种在其后代中的发育”——是对杂交种性状在亲代和后代之间的传播和分布的逐步描述。难道我们不应该恢复孟德尔当之无愧的称号——遗传学之父？

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part5：Acknowledgement

I express my thanks to two very special people who never stinted in their support: to my daughter Dianne who, with great effort, taught me to see the computer as a friend and not some mechanical fiend, and to my son Jack, who was my patient and gallant sounding board.

我要感谢两位特别的人，他们从不吝啬对我的支持：我的女儿黛安（Dianne）和我的儿子杰克（Jack），前者付出了巨大的努力，教会我把电脑当作朋友而不是机械恶魔，后者则是我耐心和勇敢的传声筒。
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A very grateful thank you goes to Barbara Wakimoto and Dan Lindsley, who prodded me into turning some scattered ideas into a coherent whole. There can, however, be only one dedication—for Larry.

还要感谢Barbara Wakimoto和Dan Lindsley，是他们鼓励我把一些零散的想法变成一个连贯的整体。此外，若还可以，我还想感谢Larry。
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