Hamrick (2002) contested the conclusion of our recent article on evolutionary constraints on digit numbers that in tetrapods limb reduction usually occurs via arrest of the initial development followed by degeneration (Galis et al 2001). Firstly, we agree with Hamrick that we unfortunately illustrated this phenomenon with the wrong figure: the digits in the hand of Didelphis marsupialis are indeed not reduced. We could have chosen many good examples in mammals (e.g., Fig 1), and we apologize for not having done so. Fortunately, our other two illustrations of the phenomenon are good examples of the transient presence of reduced digits in amphibians (Fig. 2). Furthermore, Hamrick (2002 in press) contested the embryonal presence of a digit I Anlage in the pig (Sus scrofa), because he could not find such Analgen in his serial sections. However, Baur (1884), Emery (1891, in Braus 1906), and Schmidt-Ehrenberg (1942) all have documented digit I Anlagen in the pig. In addition, both Schmidt-Ehrenberg (1942) and Holmgren (1952) confirm the presence of digit I in another artiodactyl with even more reduced digits, the cow (Bos taurus), and illustrate this with particularly clear drawings of the digit I Anlage (Fig. 1). The transient presence of these digits shows that reduction occurred via developmental arrest followed by degeneration. How general is this evolutionary mechanism of digit reduction?
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机译：哈姆里克（Hamrick（2002））对我们最近关于数字限制进化的文章的结论提出了质疑，在四足动物中，肢体减少通常通过阻止最初的发育继而发生变性而发生（Galis et al 2001）。首先，我们同意哈姆里克（Hamrick）的观点，不幸的是我们用错误的数字来说明了这种现象：确实没有减少Didelphis marsupialis手中的数字。我们可以在哺乳动物中选择许多好的例子（例如，图1），对于没有这样做，我们深表歉意。幸运的是，我们对这种现象的其他两个说明是两栖动物短暂出现数字减少的很好例子（图2）。此外，哈姆里克（Hamrick，2002年出版）对猪（Sus scrofa）中的手指I Anlage的胚胎存在提出了质疑，因为他在连续的切片中找不到这种Analgen。但是，鲍尔（Baur，1884年），埃默里（Emery，1891年，布劳斯（Braus，1906年））和施密特·埃伦贝格（Schmidt-Ehrenberg，1942年）都记载了猪的I Anlagen数字。此外，Schmidt-Ehrenberg（1942）和Holmgren（1952）都证实了数字I出现在另一个数字减少的偶蹄动物中，即母牛（Bos taurus），并特别清晰地画了数字I Anlage（图。1）。这些手指的短暂出现表明减少是通过发育停滞然后是变性而发生的。这种数字减少的进化机制有多普遍？
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