502 COMPARATIVE ANATOMY AND PHYSIOLOGY. 



affects the ova, and the green the spermatozoa. Before 

 long we may hope to see this method of investigation 

 applied to other problems of a like nature. 



In the Gastropoda we not unfrequently meet 

 with a hermaphrodite arrangement, and this even 

 among the lowest forms ; in Proneomenia Hubrecht 

 has observed differences of colour in different parts of 

 the elongated and double generative gland ; in spirit 

 specimens the light-yellow portions were found to be 



ovarian, and the brown- 

 ish - grey parts spermi- 

 genous. Here, again, we 

 note just the same kind 

 of development as we 

 have seen before; the 

 germinal epithelium gives 

 rise to ova in one region, 

 and spermatozoa in an- 

 other. 



In the higher Gastro- 

 pods we again often find, 

 as in the snail, a " her- 

 maphrodite gland," 

 and here, too, the male and female products are devel- 

 oped in different portions of the same genital area, from 

 cells which were primitively similar in character ; the 

 spermatoblasts sometimes become free from the wall 

 at an early stage (Fig. 208), and in some cases the wall 

 of the gland is produced into a number of pouches. 

 From the common generative gland, or ovotestis, 

 there leads off a common duct. 



In those Gastropods that are not hermaphrodite, 

 and in the Cephalopoda, where, too, the sexes are 

 separate, there is very generally a close resemblance 

 between the male and female essential organs, remind- 

 ing one altogether of what we have already noticed in 

 the Lamellibraiichiata. 



Fig. 208. Follicles of the Ovotestis 



of Helix hortensis. 

 oo, Ova ; ss, spermatoblasts. 



