PRODUCING ACCRETE EMBRYOS FROM ONE EGG 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 



FIG. 71 



then continue to develop into gastrulse and plutei. I wish 

 to emphasize especially that both embryos develop from the 

 beginning as entire morulse and blastulse, 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 



