NO. 1788. 



NORTH AMERICAN ERGASILID.^— WILSON. 



303 



also somewhat enlarged in diameter at the center, which gives them a 

 peculiar crenulated appearance. This structure shows more dis- 

 tinctly in the Ergasilus male (E. chautauquaensis) than in Bomolochus 

 {B. solex), but this seems to be the result of the greater transparency 

 of the former rather than of any marked structural difference. Owing 

 to the lack of material it has been impossible to determine with cer- 

 tainty whether there is any loop (epididymis, Ilertog) in the vasa 

 deferentia corresponding to that found in Cyclops and other free 

 swimmers. 



The bodies of the limited number of males examined by the author 

 have been too opaque to show up the internal anatomy with any 

 degree of distinctness. The testes could be located because they 

 were opaque enough to show as dark spots, but the transparent ducts 

 leading from them were so nearly invisible for 

 much of the distance as to leave it in doubt whether 

 they formed a loop or not. 



In Bomolochus solese the semen receptacle is some- 

 what cigar-shaped, and occupies practically the 

 whole of one side of the fifth segment and the an- 

 terior seven-eighths of the genital segment. The 

 posterior end of the receptacle is evenly rounded 

 and projects strongly from the lateral margin of the 

 genital segment near its distal end. The diameter 

 of the receptacle is about uniform throughout the 

 genital segment, but when it passes forward into 

 the fifth segment it narrows rapidly into a cone 

 whose apex falls just behind the anterior margin of 

 the segment. 



This apex passes insensibly into the vas deferens 

 at a point much nearer the mid-line than the lateral 

 margin of the segment. In the male of Ergasilus 

 cliautaucjuaensis the semen receptacles are relatively much shorter and 

 wider, and more ovate m shape. They occupy in the genital segment 

 only the anterior three-fifths, and on passing into the fifth segment 

 taper rapidly down to the diameter of the vasa deferentia (fig. 26). 



Each semen receptacle contains one or more spermatophores, 

 ready to be extruded and fastened to the body of the female. Each 

 spermatophore consists of an enlarged body, ovate or ellipsoidal in 

 shape, and a long narrow^ duct or tube leading from it, very similar to 

 those described by Gruber and others for free-swimming forms. So 

 far as observed each spermatophore is fastened to its own side of the 

 genital segment of the female and there is no crossing of the tubes as 

 in many of the other parasitic forms. Furthermore it is only rarely 

 that a female is found with these spermatophores in position. Out 

 of considerably over five hundred specimens of females belonging to 



Fig. 26.— Genital seg- 

 ment or MALE Erga- 

 silus CHAUTAUQUA- 



iiNsis, showing 



SPEKM RECEPTACLES. 



