山椒魚幼生の指間突起の生成機構 : 特に他種所属器官の誘導に就て(豫報)

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In Hynobius larvae there is a special interdigital process. which is not found in other urodeles. As the limb develops, the process at first grows, but it soon begins to degenerate to disappear completely between the lst and the 2nd digit at about the stage, when the 4th digit comes to appearance (fig. 2). The process is thus a larval organ. In order to analyse the mechanism of formation of this process, the ectoderm of the presumptive fore-limb region of Triturus larvae at the tail-bud stage was replaced unilaterally with a piece of ectoderm taken from the abdominal region of Hynobius of about the same age (fig. 1). In some cases, the limb of the operated side is suppressed to develop (fig. 3), or differentiates imcompletely (fig. 6). But, whenever digits differentiate more or less completely, there appears also at the tip of the limb a process, which no doubt represents the interdigital process peculiar to Hynobius. As in normal Hynobius larvae, the process at first develops, then it begins to degenerate and disappears between the 1st and the 2nd digit. The disappearance occurs at the stage, when the 4th digit begins to appear. From this we can say, that the limb mesoderm of Triturus is itself capable of inducing the interdigital process peculiar to Hynobius. In the normal development of Triturus, the process does not appear because of the lack of competency in Triturus ectoderm to form such a process. In the case of xenoplastic induction, SPEMANN and SCHOTTE (1932) have assumed that the behavior of ectoderm is not determined in detail, but determined comprehensively by the morphogenetic stimuli of the region. In our experiment the interdigital process formed by the transplanted ectoderm is influenced, in size as well as in podition, by the host mesoderm. Its disappearance, too, coincides temporally with the appearance of the 4th digit of the host. These results together with those of SCHOTTE and EDDS (1940) lead us to suppose that, to a certain extent, the ectoderm is determined in detail, spatially as well as temporally, by the underlying mesoderm. The interdigital process is by no means a purely ectodermal formation. Its interior is filled with mesenchyme, which is mesodermal in origin. The fact, that the transplanted Hynobius ectoderm forms on Triturus a typical interdigital process, indicates that the limb pattern is not determined solely by mesoderm nor solely by ectoderm, but by the interaction or rather the cooperation of these two germ-layers.
1941-08-15

山椒魚幼生の指間突起の生成機構 : 特に他種所属器官の誘導に就て(豫報)

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