1^92.] OF THE GENUS PERICH^TA. 161 



single row present at the posterior boundary of the clitellar region, 

 which belong therefore to segment xvi. ; it is at this point that the 

 thick chtellar epithelium ceases. The seta? do not form a continuous 

 ring round that segment (the xvith) ; they are visible only upon 

 the ventral surface and are developed for an equal distance on either 

 side of the ventral median line ; they extend for a distance of about 

 one quarter of the entire circumference of the segment. The 

 clitellar setse are quite obvious without having recourse to a micro- 

 scopical investigation of the integument, since the thick clitellar 

 epithelium is much broken along the line of their emergence. The 

 setse themselves do not appear to present any differences in shape 

 from those which are found in other parts of the body ; they may 

 perhaps be a trifle smaller, but there is no such differentiation as 

 occurs, for example, in Perichata houlleti. The most careful search 

 failed to show any setae on either of the two remaining segments of 

 the clitellum : in one specimen I counted 20 setse on segment xvi. ; 

 in another there seemed to be rather fewer, but there was no per- 

 ceptible variation in the length of the line occupied by the setae in 

 different individuals. 



I have been particular in calling attention to the characteristics of 

 the clitellum, not only because the points to which I have directed 

 attention are of specific importance, but also for the special reason 

 that they serve to discriminate Perichaeta bermudensis from Perichceta 

 aspergillum. I was at first inclined to regard the species de- 

 scribed in this paper under the name of Perichceta bermudensis as 

 being identical with Perichaeta as[>ergillum. The latter was first 

 described by Perrier ' as being " sans designation d'origine." As I 

 received a few years ago some Earthworms collected by Vlr. Shipley 

 in the Bermudas which seemed to be P. aspergiUum, I considered 

 that the present species was the same, as the individuals agreed, on a 

 superficial inspection, with Perichceta aspergiUum. However, in 

 Perrier's description of P. aspergiUum there are characters mentioned 

 which appear to show that I am right in regarding Perichaeta ber- 

 mudensis as a distinct though closely allied form ; in the figure " 

 illustrating Perichceta aspergiUum setae are figured upon aU the 

 segments of the cUlellum ; but in the text the matter is left a little 

 obscure. M, Perrier says (p. 120), " Je n'ai vu sur la ceinture que de 

 faibles traces . . . . des ceintures de soies." 



The great difference in size may possibly also be a valid specific 

 difference ; no doubt this character is one which has to be used with 

 special caution in the case of Earthworms. There are other points, 

 too, which I shall call attention to in referring to the characters 

 offered by the male generative pores and the spermathecal pores. 



The dorsal pores commence, as in Perichceta aspergiUum, between 

 segments x./xi. 



The oviducal pore lies upon the middle veutral line of segment xiv. 



' "Recherehes pour servir a I'histoire des Lombrioiens terrestres," Nouy. 

 Arch. Mus. t. viii. p. 5. 

 ■^ Loc. ait. pi. iv. fig. 71. 



Proc. Zool. Soc— 1892, No. XI. 11 



