I So 



C. M. CHILD. 



blastula wall and of all degrees of reduction, even to complete 

 obliteration, of the blastoccel by continued mass ingrowth of the 

 thicker parts of the wall instead of, or in addition to immigration 



4 



7 8 



of single cells. The thickened region is a solid cell mass, usually 

 without distinct boundary between ectoderm and entoderm. 

 Fig. 6 represents a condition observed thus far chiefly in LiCl in 

 which the blastocccl is completely obliterated by cells and basal 

 emigration is occurring. 



In all these modified forms development is retarded and 

 locomotion is much slower than normal. Many of these in- 



