PLATE 5 



EXPLANATION OF FIGURES 



All figures at a magnification of 1024, except figures 44 and 45, which are 

 X 681. 



41 Two primordial female cells (A) at periphery of adult testis. These 

 cells often become very much changed in appearance during the male phase, as 

 figure indicates. Spermatogonia (spg) and early spermatocyte (spcl) also 

 shown. X 1024. 



42 Section at periphery of testis during retrogression. Cytoplasm of periph- 

 eral syncytium reaching out to join to cells in lumen. X 1024 Length of 

 specimen, 8 mm. 



43 Inclusion of sperm heads (esp) and apyrene sperm (asp) in peripheral 

 syncytium, which has become very much thicker than in former condition. 

 While sperm, spermatids, etc., are being taken up into the wall of the gonad, 

 some of the peripheral nuclei show the appearance of those in this figure. Ap- 

 parently the tension of the nuclear membrane is relaxed in some regions and 

 the contents of the nucleus becomes bulged out. This probably explains the 

 distorted shape of most nuclei in figure 45 where the degenerate products have 

 been dissolved. X 1024. 



44 Section through part of degenerate male gonad from which all testis 

 cells have absorbed. Peripheral syncytium deep and vacuolar. X 681. Length 

 of specimen, 11 mm. 



45 Section through strand of degenerate male gonad. Nuclei at periphery 

 distorted. X 681. Length of specimen, 9 mm. 



46 Section through different part of same gonad as figure 43. Sperm heads 

 embedded in wall. X 1024. 



47 Section through peripheral wall of gonad during transition period. 

 Specimen from which figure was drawn was taken as adult male (15 mm.) from 

 a colony; during thirty-seven days after transferring to a second hermit shell, 

 penis entirely degenerated, and gonad was found inactive, when sectioned. 

 X 1024. 



48 Later stage. Part of syncytial wall becomes dissolved, while part con- 

 denses about follicles nuclei. Cytoplasm of germ cells becomes more clearly 

 defined. X 1024. Length of specimen, 13 mm. 



62 



