Propucine ACCRETE EMBRYOS FROM ONE Ea@a@ 305 
cleavage sphere then developed in the normal way (Fig. 71), 
and finally a cleavage plane appeared in the extraovate 
(Fig. 72). 
In this way the nucleus becomes distributed through the 
egg. The further development is simple. The external 
form of the double sphere is maintained, while both parts 
divide into smaller cells; each of the two spheres forms a 
separate blastula cavity, which may communicate in certain 
cases, although they do not do this as a rule. The spheres 
then continue to develop into gastrule and plutei. I wish 
to emphasize especially that both embryos develop from the 
beginning as entire morule and blastule, and that no half- 
formation of any sort appears. In other words, the develop- 
ment goes on as if two independent eggs had been laid side 
_ by side, or had been glued together, and each had cleaved 
and developed entirely independently of the other. The 
protoplasmic connection of the two double embryos acts, 
however, differently from the way the gluing together of 
two eggs would do, as is evidenced by the deformities in the 
skeletal parts of the two plutei. 
3. I have repeated these experiments with eggs in various 
stages of cleavage. Under these circumstances, also, the 
protoplasm always flows out in such a way that the cells 
remain joined together and double spheres are formed. I 
always obtained the same results, namely, double or multiple 
embryos. Only in the eggs which had developed very far— 
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