POLYEMBRYONIC DEVELOPMENT IN TATUSIA 639 



Furthermore, it was observed in at least three living specimens, so 

 that there can be no doubt but that during the early history 

 of the embryonic buds, Nos. II and IV are more highly devel- 

 oped than their mates I and III. And what else can this mean 

 than that phylogenetically the former pair should precede the 

 latter. 



This obvious difference in size does not last indefinitely, and 

 indeed is no longer discernable after the embryonic rudiments 

 have become slipper-shaped (fig. 5) . 



That primary buds may also be precursors of secondary buds 

 hi Mulita is, I believe, to be inferred from the work of Fernandez 

 ('09) on that form. Unfortunately, he has but a few scattered 

 stages at his command, and therefore was not able to give us a 

 full history of the development of the embryonic rudiments. 

 His specimen 46, which is the one next to his youngest stage 

 (corresponding to Specimen .233), already has embryonic rudi- 

 ments fully as well developed as those in Specimen No. 226 (plate 

 11). Nevertheless, in speaking of the relation which exists be- 

 tween the ectoderm of the common amnion and that of the 

 embryonic diverticula in this specimen, he makes the following 

 significant statement, "Der Cervix uteri zu, d.h. tiber dem Anfang 

 der Medullarplatte, ist das Amnion keines Tieres geschlossen, as 

 steht vielmehr durch eine sehr weite Offnung mit dem Amnion 

 eines oder mehrerer Nachbartiere in vollkommener Kommunika- 

 tion. ' ' 12 Again in the same paragraph he says, ' ' Das Amnion eines 

 Einzelembryo kann sich auch direkt in diese Blase offnen, ohne 

 vorher mit den Amnia andrer Embryonen in Verbindung getreten 



zu sein. " 



If we pass from these two statements to an examination of his 

 figures 1 and 2 (plate 17), which are photographs of vesicles show- 

 ing well-formed embryos, we shall find further evidence of this 

 same nature. The specimen shown in figure 1 is from a vesicle 

 containing 11 embryos, six of which appear in the photograph. 

 On account of the advanced stage of development, the evidence 

 that two embryos have come from a common diverticulum must 

 be sought in the relation of the amniotic canals to the common 



12 Loc. cit., p. 314. 



