ON THE OCELOMj GENITAL DUOTS, AND NEPHUIDTA. 487 



In Dinopliilus apatris, Korschelt has described flame-cells 

 which he believed to be connected with a longitudinal canal 

 opening posteriorly (66). E. Meyer, however, has figured in 

 D. gyrociliatus five pairs of typical closed nephridia, or 

 pronephridia, ending in flame-cells internally, and disposed 

 metamerically according to the outer signs of segmentation (80) . 

 Harmer (46) describes five pairs of very similar nephridia in 

 the female D. taenia t us. In the male there are four pairs of 

 nephridia, perhaps with internal openings.^ 



The testes are a large right and left sac, which fuse across the 

 median line ; as Harmer himself says, it is '^possible that in the 

 connective-tissue lacunae of the body of Diuophilus we have the 

 representative of the so-called 'primary body-cavity,' whilst in 

 the fully developed male the 'secondary body-cavity' is repre- 

 sented by the cavity of the testis, with which the funnels of the 

 vesiculse seminales are connected." It might be added that these 

 funnels, which form the inner openings of the sperm-ducts, have 

 all the appearance of true peritoneal funnels, comparable to the 

 genital ducts of the Platyhelminths, and the other groups 

 already spoken of. 



The paired ovarian cavities appear to be provided with only 

 very degenerate ducts, reduced to mere pores in D. vorticoides 

 and D. apatris (compare the Archiannelida and the female 

 ducts of certain Oligochseta such as the Enchytroeids). 



The structure of Dinophilus might be explained in one of 

 two ways. Either it has acquired a number of nephridia, 

 whilst retaining the primitive single pair of genital follicles ; 

 or it is a degenerate form which has lost its metamerically 

 repeated genital follicles, whilst retaining a number of separate 

 nephridia. Our present knowledge does not enable us to con- 

 clude for certain which of these explanations is the correct one.^ 



Histriodrilus Benedeni (Histriobdella homari) may 



' The fifth pair is possibly, according to Harmer, represented by the distal 

 portiou of the genital ducts leading to the penis (compare with certain Poly- 

 chseta where the nephridium fuses with the peritoneal funnel). 



' In a paper which has just appeared Schimkewitsch describes a ladder- 

 like nervous system, and traces of segmentation in the developing mesoblast 

 ('Zeit. f. w. Zool.,' Bd. lix, 1895). 



VOL. 87, PAKT 4. — NEW SEli. K K 



