ON MONOPYLEPHORUS LIMOSUS. 



35 



"A 

 dp 



sp _ 



spth.p 



appears that his ' slender duct-like portion ' corresponds to my 

 ' transversal bridge.' I have had no opportunity so far to study very 

 young specimens in sections, but in the younger, though full-grown, 

 specimens I have observed, in which the sperm-cells have been 

 just liberated from the testes and no spermatozoa have yet been 



developed, the spermiducal chamber lias 

 not attained its full size and much 

 space is left between the summit of the 

 dorsal portion of the lateral horn and 

 the body wall, the atrium is not much 

 - hp swollen and the prostate gland cells are 

 less well differentiated from the ordinary 

 peritoneum. These facts seem to me to 

 suggest that with the gradual comple- 

 tion of the spermiducal chamber the 

 atrial duct portion is gradually lifted 

 up into the dorsal region of the body 

 and that the swelling of the atrium is 

 a subsequent event. If this is true, 

 then the conclusion is justified that the 

 more ventrally the atrial duct portion 

 lies the younger is the specimen. So 



JPig. 29. 

 Spermatheca. xl50. A, anterior l SnS P eCt that HaTAI ^ ^sMj haVÔ 



view, b, dorsal view, a -anterior, p re p a red his descriptions and figures 



p — posterior, dp— duct portion, sp 



—saccular portion, spth. p-sper- from younger specimens, as already 



mathecal pore, hp-hypodermis. . suggested previously when describing 



the clitellar hypodermis. 



4). Spermatheca. The organ lies for the most part in the 

 anterior half of segment X under the intestine and between the 

 testes. It consists of a somewhat conical common duct and paired 

 sigmoidal saccular portions (figs. 25, 29, 30). While the ova are 



sp— - 



dp- 



