168 



Chridmns Island. 



I could not see exactly where the vas deferens joins the prostate, 

 hut I have little doubt that the connection between both structures 

 will be found to be the same as that which has been described by 

 Akira Jizuka for P. matsushimensis. 



Our species seems to be closely allied to P. insularis (Rosa), 

 which I first described from specimens obtained in the Aru 

 Islands,^ and which has been more recently found also at Ceylon 

 (Michaelsen).^ Still, a marked difference between the two species 

 exists, as in the sperm athecse of P. insularis both Michaelsen and 

 I failed to find any diverticulum. Our specimens were not fully 

 mature, but on the hypothesis of an identity between these two 

 species it seems highly improbable that even in a series of sections 

 no traces could be found of an organ which in the adult reaches so 

 great a development. Moreover, in the descriptions of P. insularis 

 no mention is made of a ventral sucker. 



Another allied species is undoubtedly P. matsushimensis, for 

 a clear description of which we are indebted to Akira Jizuka.^ 

 However, this Japanese Pontodrilus seems to be really different 

 from our species. 



First, it is a larger species than ours, as its length ranges from 

 90 to 110 mm., with a diameter of 3-3'5mm. ; while our specimens, 

 with a diameter, too, of 3 mm., have only a length of 43-47 mm. 

 Besides, it may be noted that the clitellum of P. matsushimensis is 

 described as being well developed all round the body (and the same 

 is shown by the figures), whilst in our species the clitellum is 

 distinctly saddle-shaped. Finally, the appearance of the prostate 

 is (so far as one can judge from the figures) somewhat different. 



2. Perichaeta brevis, D. Eosa (1898). (Figs. 3, 4.) 



D. Rosa: Ann. Mag. Nat. Hist. [7], vol. ii (1898), p. 283, pi. ix, figs. 6, 7. 



4 



TerichtBta brevis, D. Eosa (1898). 



Fig. 3. Sperm-sacs {vs.), sperm-reservoirs (es.), and diverticulum {cs.div.). 

 ,, 4. Spermatheca. 



^ Ann. d. naturh. Hofmuseum, "Wien, Bd. vi, 1895. 



' Mitth. aus. d. naturhistor. Museum, xiv (Hamburg, 1897). 



^ Annotationes Zoologicee Japonenses, vol. ii, pars 1 (Tokyo, 1898). 



