GERM CELLS OF COELENTERATES 9 



each such group of egg cells in that place than with a single 

 germinal zone at some distance and later migration of eggs into 

 the places of ripening and development. 



One other point of general interest comes from this study of 

 entire stems or parts of colonies. At A in figure 1 there is a 

 group of egg cells in the stem, the same is true in region B, and 

 between the two is a hydranth whose stalk contains eggs. Gon- 

 ophores are not present here, but these are regions where 

 gonophores would have developed in the living colony. The 

 evidence for this is easily obtained by a study of gonophore for- 

 mation in different colonies. Probably the simplest explanation 

 for such an arrangement is the suggestion of C. W. Hargitt ('04) 

 that the presence of a group of egg cells may be the stimulus for 

 the formation of the gonophore. 80 far as I have observed in 

 Eudendrium ramosum, groups of germ cells are always present 

 before a gonophore begins its development. 



Study of sections. The study of stained and cleared portions 

 of the colony gave a clear understanding of the relative position 

 of egg cells in stems, hydranths, and gonophores, and of the num- 

 bers and sizes of egg cells, but did not permit a positive deter- 

 mination of the place and method of origin of such cells. It was 

 also impossible to distinguish small egg cells and gland cells, 

 since all deeply staining cells had much the same appearance. 

 These difficulties should not obtain in sections, hence various 

 parts of the colony were sectioned and studied. 



A longitudinal section through the stem, just proximal to a 

 terminal hydranth, is shown in figure 7, one-half the width of the 

 section being represented. In the entoderm a typical egg cell 

 which has undergone some growth is shown at ov, lying deep 

 in the entoderm against the supporting layer and separated 

 from the enteric cavity by entoderm cells. Its cytoplasm is 

 composed of uniformly distributed granules, large and deeply 

 stained; the nucleus is large, with a distinct nucleolus, and con- 

 tains a relatively larger amount of chromatin than the regular 

 entoderm cells. The chromatin is distributed chiefly about the 

 nuclear membrane with a small amount forming a network in the 

 nuclear sap. These characteristics are more or less applicable 



