THE ANATOMY OP ONCHOLAIMUS VULGARIS, BAST. 145 



The fact that in parasitic Nematodes the cavities form 

 highly convoluted tubes of great length should not be allowed 

 to obscure this truth. In the forms which I have described 

 we have a series. It commences with the simple gonocoel 

 found in the immature female or mature male of Oncho- 

 laimus vulgaris; next^ in the mature female the gonocoel 

 is slightly more complex ; there is a narrow conical outgrowth 

 from the original cavity, which is represented by the ovarian 

 csecum ; finally, in A. clavata the entire gonocoel has 

 become enormously elongated and convoluted. 



The canse for this latter development is obvious — viz. the 

 call for an enormous increase in the reproductive products on 

 changing from a free to a parasitic life. 



In the description of Oncholaimus vulgaris and 

 Ascaris clavata above I have refrained from the use of 

 the terms " gonocoel " and " gonoduct/' since I did not wish 

 unnecessarily to bring theory into the strictly descriptive part 

 of my article. I wish now, however, to repeat that I believe 

 that the "testicular" and "ovarian regions" correspond 

 accurately with the male and female gonoccels respectively, 

 and that the remaining portions of the genital tracts (uterus 

 and vagina and ductus ejaculatorius in Oncholaimus 

 vulgaris; oviduct, receptaculum seminis, uterus and vagina, 

 vas deferens, vesicle, and ductus in Ascaris clavata) 

 correspond with the gonoducts. The wall of the former 

 consists of an exceedingly fine squamous epithelium only; in 

 the wall of the latter the epithelium is cubical or columnar 

 (except when the duct is much distended), and there are 

 other coats. 



Comparative Morphology of the Gonenteric Canals. 



The only organ in any way similar which has been pre- 

 viously described in Nematodes is the remarkable '' Rohren- 

 fonnige organ" with its ducts, found by De Man (12) in 

 Oncholaimus fuscus. This consists of a tube lined by 

 epithelium, lying dorsally in the body-space, communicatino* 



