26 HARLEY N. GOULD 



The foregoing development is the normal one and leads to the 

 formation of the adult atypical sperm shown in figures 39 and 61 ; 

 but this development does not always run through to comple- 

 tion in the manner described; for at any point in the develop- 

 ment a peculiar sort of degeneration may set in. It results in a 

 swelling of the cell body, a change in the staining reaction, and 

 often the formation of large vacuoles. Some of the results of 

 this digression from normal development are shown in figures 53 

 to 59 (on a smaller scale than figures 24 to 39) . There is always 

 a marked swelling of the cell body. The cytoplasm of these 

 swollen and distorted cells is more homogeneous than the cyto- 

 plasm of the normal apyrene cells and takes a deeper eosin or 

 light green stain. It is not true that the cells are dead; for 

 when the contents of the testis of a live Crepidula are trans- 

 ferred to a slide, some of the distorted apyrene spermatosomes 

 are seen to be in rapid movement. It is hard to escape the con- 

 clusion that this change is a purposeful one, and that the meta- 

 morphosed cells may have some nutritive function. 



Some of the abnormal apyrene spermatosomes in Crepidula 

 resemble the normal ones figured for other Molluscs. For in- 

 stance, cells have been occasionally found on the slides which 

 are extremely like the spermatosomes in Strombus (Reinke) 

 when the albuminous bodies are in process of formation; and 

 figure 58 has a very noticeable resemblance to Kuschakewitsch's 

 figure 199 of the nearly adult apyrene spermatozoon of Verme- 

 tus. It is believed that this digressive method of development 

 of the atypical cells in Crepidula is not a casual matter, a mere 

 failure to complete the normal course, but that it is the expres- 

 sion of principles working out normally in other forms. 



The abnormal apyrene spermatozoa are only occasionally 

 found in the seminal vesicle with the normal apyrenes. The 

 few that are present there show that degeneration has set in 

 late in development. 



The cells of the apyrene series in the testis are very much 

 fewer than those of the eupyrene series. In the seminal vesicle 

 there are about 6 eupyrenes to 1 apyrene. No apyrenes have 

 been found in the seminal receptacles of the female. It is not 



