296 3%° SECTION — VERTÉBRÉS (ANATOMIE) 
independent characters (2. e., in the developing embryo and in the capsule 
secreted by the oviduct) continue to coïncide during selection of fortui- 
tous variations in the different stages in development, so that in the end 
a species might continue to survive? Nor is it easy to understand its 
evolution on Lamarckian grounds, since a complete egg capsule would 
hardly have been moulded around an embryo when the latter was already 
so perfectly grown that the elaborate capsule could have been but useless. 
Third : In the fertilization of the ege. Polyspermy occurs, but judging 
from stages in the male pronuclei the sperms do not enter the germ 
simultaneously : and thus fertilization takes place during an appreciable 
interval of time. Moreover, the supplemental sperm nuclei undergo at 
once amitotic division, whereas in sharks amitotic division follows only 
after a series of gradually changing mitotic divisions. 
Fourth: In segmentation. Cleavage lines appear only after several 
divisions of nuclei have taken place. In this regard Chimæra behaves 
somewbhat like the highly specialized ray among recent Elasmobranchs. 
Fifth : In the precocious growth of the embryo. An embryo which, 
with its attached blastoderm suggests stage B (BaLrour) in the shark, is 
intrinsically much more perfectly developed e. g. in the details of its head, 
heart region and tail. In spite of minute size, it resembles more closely 
the shark stage D. The chimæroid embryo tends, accordingly, to assume 
its ordinal characters at a very early period, and in this regard it is to 
the shark as the teleost embryo is to the ganoïd. 
Sixth : In the early arrangement for the nutrition and development 
of the blastoderm. for it is found that the conditions of the periblast are 
remarkably complicated. Thus, it is found that even in an early stage of the 
blastoderm, one corresponding to B in shark, the yolk nuelei are already 
widely different in different subgerminal regions. Especially clear is the 
way in which yolk cells are contributed to the blastoderm. Into the peri- 
phery of the latter are sometimes budded elements of such large size 
that they can in no way be confounded with the cells of the blastoderm. 
These cellular increments, moreover, cannot, I am convinced, be confoun- 
ded with the so-called primordial germ cells, since I have traced their 
fate and found that in the majority of cases their descendants contribute 
to the development of the vascular system. Furthermore, in this preco- 
cious development of the blastoderm, the laws both of the germ layers 
as well as of the behavior of amitotic nuclei appear to have undergone 
remarkable inversion. In the first regard, for example, there is clear 
testimony that the vascular system is in part (I refer particulary to the 
vessels which arise hear the middle of the blastoderm) formed from ecto- 
derm. In the second regard, in a large number of cases nuclei which 
have been undergoing amitosis pass into the blastoderm and even in 
certain cases continue for a time to undergo amitosis in the blastoderm. 
LT RSS 
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