198 J. H. ASHWORTH. 



(2) In many cases one of these cells, surrounded by a thin film of 

 mesogloea, may be seen enclosed in a follicle of endoderm projecting 

 from the edge of the mesentery. These are exactly similar to the 

 neighbouring follicles which contain spermatozoa in various later stages 

 of development. 



(3) The nuclei of most of these cells are large and spherical, more 

 vesicular than the nuclei of the adjacent endoderm cells, and resemble 

 the nuclei of the genital cells (see PI. XXII., Fig. 30). 



(4) The ripe spermatozoa are situated in a follicle covered by a thin 

 mesogloeal lamina, as well as by the endoderm cells outside this, i.e., 

 the ripe spermatozoa are situated in the same layer as these cells, viz., 

 in the mesogloea. 



The migration of genital cells from the endoderm of the mesenteries 

 into the mesogloea is similar to that described by 0. and R. Hertwig in 

 Actinirv ('Die Actinien,' Jena, 1879, p. 95, and PL 7). 



Endoderm (PL XXI.). 



The endoderm cells lining the coelentera and the cavities of the 

 tentacles have a similar structure throughout the colony. They are 

 cubical or columnar, and contain many small vacuoles which give the 

 protoplasm a recticulate appearance. 



Cells which bear Ftajella (Figs. 20 — 25, 27). — Among the ordinary 

 endoderm cells there are numerous cells, the inner or free end of which 

 is produced into a long process, which is from four to eight times as 

 long as the basal portion of the cell. This process may be slender or 

 moderately stout, and its length may vary in different specimens from 

 '015 mm. to *12 mm. The basal part of the cell from which the 

 process arises has the reticulate protoplasm of an ordinary endoderm 

 cell, and the nucleus of the cell is situated in this portion, 

 The process is not vacuolated, and for the greater part of its 

 length its protoplasm exhibits a homogeneous or very finely 

 granular structure. Its basal part, i.e., the part in continuity with the 

 vacuolated portion of the cell, stains deeply with hematoxylin, and in 

 most cases shows very faint longitudinal striations which are visible 

 only in the proximal third of the process. 



The processes usually taper towards their free end, but in one 

 instance this end is slightly broadened and flattened (Fig. 25 A). In 



