THE PRODUCTION OF GRAFTED EMBRYOS. 87 



111 a large number of instances a true fusion occurred during 

 the blastula stage, as recognized by the continuous ectoderm and 

 common blastoccele. In Fig. 36 a blastula is shown with a 

 part extruded beyond the fertilization membrane. In Fig. 37 

 the blastula is pinched together near the middle. A whole and 

 a half egg have been fused in the formation of the single blastula 

 shown in Fig. 38. At least two eggs have united in Fig. 39. In 

 Fig. 40 an egg a half egg and a quarter egg have so fused. 

 Figs. 41, 42 and 43 represent other fusions of two or more eggs 

 into single giant blastulae. Figs. 44 and 45 are interesting because 



FIG. 49. 



they suggest how a common blastoccele may be formed by the 

 breaking down of the separating wall. 



The clusters were not necessarily linear. Triangular groups 

 like Figs. 45, 46 and 47 were not uncommon. Other clusters 

 were quite irregular as in Figs. 48 and 49. A large cluster like 

 the one shown in Fig. 49 was more frequently composed of 

 agglutinated eggs or a complex of fused and agglutinated eggs; 

 smaller clusters also included agglutinated and fused members 

 shown in Figs. 50, 51, 52, 53, 54, 47 and 48. 



Fused blastulae tended to lose their individual identity by the 

 continuity of their common layer of cells, by the disappearance 

 of their inner separating walls and by the closer approximation 

 of the separate blastulae. These processes continued until a 

 spherical or almost spherical giant blastula was produced, in 

 which it was difficult or impossible to distinguish the component 

 members, as in Figs. 55, 56 and 57. 



