NOTES ON THE ANATOMY OF DINOPHILUS. 57 



Dinophilus is really less considerable than would appear from a com- 

 parison of Hatschek's figures with my own. 



In many of its features Polygordhis differs from Dinophilus far 

 more than does Protodrilus. This is sufficiently obvious by such 

 characters of Polygordius as the fusion of the ventral nerve-cords, 

 the absence of a muscular oesophageal appendage, the form of the 

 nephridia, the greater development of the longitudinal muscles, &c. 

 (cf. Fraipont, No. 3). All these facts justify us in concluding that 

 Polygordius is less closely related to Dinophilus than is Protodrilus. 



Histriodrilus {Histriohdella) , on the contrary, is probably more 

 closely related to Dinnphilus than is Protodrilus. The similarity in 

 the nervous systems of the two genera has been already alluded to, 

 and the same general resemblances characterise the excretory and 

 generative systems. 



The arrangement of the excretory system in Histriodrilus is said 

 to differ in the two sexes. The nephridia are somewhat S-shaped, 

 intracellular tubes (unfortunately not figured by Foettinger in much 

 detail) ; it is stated that five (or perhaps six) pairs are found in the 

 male, and four pairs in the female ; their relations to the segments 

 are shown by means of woodcuts on p. 469 of Foettinger's Memoir. 

 The second nephridium was observed on two occasions to end in- 

 ternally in a ciliated ampulla. 



In the existence of structares connected with the generative 

 apparatus, and which may possibly be regarded as modified nephridia, 

 Histriodrilus again shows evidences of affinity to Dinophilus. 



In the female Histriodrilus there are two ovaries, which are more 

 or less fused posteriorly (as in D. gigas). These ovaries are situated, 

 as in Dinophilus, on the ventral side of the alimentary canal. The 

 ripe ova fall into the body-cavity, whence they are taken up by 

 the ciliated funnels of a pair of tubes which open to the exterior 

 laterally. These funnels (woodcut, p. 481 of Foettinger's paper) are 

 large, and open into the body-cavity on the ventral side of the 

 ovaries. The tubes into which the funnels lead possess a dilatation, 

 containing spermatozoa which have been presumably derived from 

 a male individual. The resemblance of these structures to the 

 vesiculae seminales of the male D. tseniatus (in which evidence has 

 been brought forward above to show that the vesicula is a modified 

 nephridium) suggests that they too are possibly modified nephridia. 



The male generative organs of Histriodrilus appear to be very 

 complicated, and their structure and functions were not thoroughly 

 understood by Foettinger. The testes are placed on the ventral side 

 of the alimentary canal, and are more or less paired in front, whilst 

 they are fused posteriorly. At the posterior end of the generative 

 segment are a pair of vesicles containing spermatozoa (Foettinger, 



