104 Proceedings of the Royal Physical Society. 



The figure which Michaelsen (taf. i., fig. 2/) gives of one 

 of the testicular lobes is rather more like what I have found 

 than the figures of Claparede or Vejdovsky. 



I could not find any cubical epithelium covering the out- 

 side of the testes, but each lobe was ensheathed in a very 

 distinct peritoneum (fig. 7), below which are delicate fibres, 

 as Vejdovsky has described. It is no doubt the peculiar 

 nature of this sheath which led Vejdovsky to regard the 

 organ as being a sperm sac and not a testis ; the presence 

 also of gregarines, which are figured by Vejdovsky within 

 the organ, lends some support to this view, since these para- 

 sites are so constantly found in the sperm sacs. The sheath 

 of the testicular lobes is closely applied at the base of attach- 

 ment (fig. 8), but towards the free extremities of the pro- 

 cesses it is separated (fig. 7), perhaps by the action of the 

 re-agents, and appears to be quite independent, thus giving 

 rise to a strong likeness to a sperm sac enclosing the develop- 

 ing spermatozoa. In spite, however, of this resemblance to 

 a sperm sac, I agree with Michaelsen that these organs are 

 testes. 



It seems to me to be possible that the large size of the 

 testes and the stout peritoneal investment render unnecessary 

 the development of special sperm sacs. 



Description of Species, 



The two species differ in their size, one being considerably 

 larger than the other. 



The larger species appears to be identical with Claparede's 

 Pachydrilus verrucosus. It agrees with that species (1.) in the 

 multifid testes attached to both sides of the septum separat- 

 ing segments 10, 11 ;i (2.) in the large vas deferens funnel, 

 which is relatively longer than that of P. crassus, but shorter 

 and thicker than that of P. ehcdensis ; (3.) in the characters of 

 the perivisceral corpuscles. ClaparMe does not remark the 

 presence of glands surrounding the orifice of the sperma- 

 theca, which exist in my specimens. The only reason which 



^ Claparede does not say distinctly that the testes are found on both sides 

 of the septum {i.e., that there are two pairs) ; it is to be inferred, liowever, 

 that this is the case, from his statement that they occupy two segments. 



