THE ANATOMY OF ONCHOLAIMUS VULGARIS, BAST. 137 



apertui'e wliicli lies in the mid-ventral line at the end of the 

 third tenth of the body. 



In preparations of the entire animal the appearance of this 

 portion varies according to whetlier it is distended or not. 

 At its commencement it contains large quantities of ova, and 

 is not to be distinguished from the uterus. Further on, how- 

 ever, it contracts, and forms a fairly thick walled muscular 

 tube, with here and there a single ovum in its lumen. 



In sections this division is also clear, the upper portion 

 thin walled, the lower thick and muscular. Histologically, 

 indeed, for about the first quarter the wall is identical with 

 that of the uterus. Then it begins to change, the epithelium 

 becomes more and more columnar, the basement membrane 

 more and more indistinct, merging on the one hand Avitli 

 the outer wall of the epithelial cells and with the partitions 

 between them and on the other with the outer muscular layer. 

 This outer muscular layer is continuous with the outer epi- 

 thelioid layer of the uterus ; it consists of circular muscular 

 fibres. 



Towards the termination there is also an internal cuticular 

 lining, continuous with the cuticle of the body wall. 



The external aperture is puckered, and, if open, would be 

 circular. Around the ajjerture the epithelium of the vagina 

 becomes continuous with the subcuticular layer of epidermis. 



Male Reproductive Organs. 



The male reproductive organs consist of a single tube, in 

 contrast to the double female tubes. In other respects 

 analogies, if not homologies, are easily demonstrable. The 

 germinal mass again is attached to the fundus, and projects 

 down the lumen. The tube is divided into a portion in which 

 development and maturation of germs take place and into a 

 portion serving merely as a passage to the exterior, the 

 former consisting of a region containing the testis correspond- 

 ing with the ovarian region, the latter of a vas deferens cor- 

 responding with the oviduct, a seminal vessel corresponding 



