414 HOLMES. [Vol. XVI. 



of all the cells. From the twenty-eight-cell stage until the period 

 of gastrulation it has remained without a single division. The 

 cleavage of the central cells is bilateral; the cell B divides 

 radially ; the cleavage of A is laeotropic ; that of C dexiotropic. 

 These divisions are followed by an equatorial cleavage of the 

 cells of the fourth quartette. The derivatives of 4^ divide first, 

 but the cleavage of the cells in the other two quadrants soon 

 follows. There are, after these divisions are completed, twenty- 

 four cells of the fourth quartette and three of the fifth ; these, 

 with the four small cells at the vegetal pole, make a total of 

 thirty-one entomeres. The entoderm cells at this stage are of 

 small and about equal size, and are easily distinguished from 

 the surrounding ectoderm cells by their yellow color. Their 

 number is increased somewhat before gastrulation has pro- 

 gressed very far, but I have not attempted to follow their 

 cleavage beyond the point just described. 



Small spheres of an albuminous substance gradually accumu- 

 late in the entoderm cells and become quite numerous near the 

 period of gastrulation. These spheres stain very darkly in 

 haematoxylin and make observation of the nuclei very diffi- 

 cult. At their first appearance, these dark bodies are found 

 also in the ectoderm; but, as development proceeds, they 

 become more and more confined to the entodermic cells. The 

 staining reaction of these bodies is much like that of the sur- 

 rounding albuminous matter in which the embryo floats, and it 

 is very probable that they are simply masses of albuminous 

 substance that has been ingested by the cells and has not been 

 chemically transformed. After invagination certain of the ento- 

 dermic cells increase enormously in size, becoming filled with a 

 transparent, yellowish substance that is little affected by stains. 

 Rabl has shown that in the end of the cells turned toward the 

 enteron there are masses of deeply staining substances which 

 he regards as material which has been absorbed by the cells, 

 but not completely transformed into the yellowish substance 

 which fills the greater part of the cell. It is doubtless the same 

 material that forms the darkly staining bodies in the Q.g^. 



The ingestion of albumin occurs in a similar manner in the 

 &%% of Limax, and has been described by Meisenheimer, whose 



