264 J. H. ASHWORTH. 



of the polyp and in the upper portions of the stem. That this 

 is the case is shown by the following : 



(1) These cells are most numerous in those parts of the 

 colony where gonads occur in greatest numbers. 



(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) Tiie nuclei of most of these cells are large and spherical; 

 more vesicular than the nuclei of the adjacent endoderm cellsj 

 and resemble the nuclei of the genital cells (see PI. 27, 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 tiie 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 

 O. and R. Hertwig in Actiniae ('Die Actinien,' Jena, 1879, 

 p. 95, and pi. 7). 



Endoderm (PI. 26). 



The endoderm cells lining the coelentera and the cavities 

 of the tentacles have a similar structure throughout the 

 colony. Tliey are cubical or columnar, and contain many 

 small vacuoles which give the protoplasm a reticulate appear- 

 ance. 



Cells which bear Flagella (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 



