EART.y OXTOOtEXETLO PJIEXOMEXA IX MAMMALS. 267 
Cervus, OviSj etc. — and particularly so in the case of the bat, 
to which Hubrecht draws especial attention, the idea that the 
formation of the amnion and the incurving of the epiblast of 
the embryonal area in Eutherian mammals may have had 
their origin in the overgrowth of the yolk by the epiblast 
after the manner of Sauropsidans as suggested by me (1908, 
p. 252 ; ref. Hubi'echt, p. 23, line 19) seems to me still to have 
some value, although no doubt at the present time the reten- 
tion of the curvature and the particular form of amnion 
formation in some mammals and not in others depends on 
various differences in present-time conditions. 
This means that the rabbit, sheep, or dog type of amnion 
formation has been derived from a type like that seen in 
Cavia, whose ancestors had the sauropsidan mode of amnion 
formation. 
The trace of such a history is perhaps to bo seen in the 
blastocyst of Capra (Asshetou, 1908). 
Allantois. 
I take it that the object of Hubrecht’s suggestions as 
regards the Allantois is the removal of the difficulty of 
imagining how the Allantois could have acquired its respira- 
tory or nutrient functions in the first place, and how it can 
have become attached to the somatopleure during early 
embryonic life in the second place, in other words, how to 
bridge over the gap between Anamnia and Amniota. 
Probably all agree that the Allantois as an organ of respira- 
tion, or respiration and nutrition, can only have come into 
being in connection with the presence of an amnion. 
Hubi’echt derives the amnion and trophoblast from an epi- 
blastic larval envelope present before and when the ancestral 
Amniote became viviparous, and as yet having small, yolk- 
less eggs. He discards the idea that the uriuary bladder 
of the Amphibian could grow out like the allantois of an 
Amniote, and suggests that the allantois is the resulting 
effect of an original connection between the splanchnic meso- 
