1892.] ON THE GENUS PERICH^TA. 153 



4. On some Species of the Genus Penchceta {sensu stricto) . 

 By Frank E. Beddard, M.A., Prosector to the Society. 



[Eeceived February 5, 1892.] 



(Plates IX. & X.) 



I have already communicated to this Society ' some observations 

 upon the family Perichsetidse and upon the generic types which may 

 be recognized in it. In the present paper I propose to describe some 

 species of PerichcBta {s. s.). I regard those Perichaetidse as referable 

 to the genus Perichceta in the strict sense in which the setae are 

 disposed in a perfectly continuous circle round each segment, being 

 generally (? always) disposed along a distinct ridge in the middle of 

 the segment ; this gives to the species of the genus a very different 

 feel from either Megascolex or Perionyx, since the setse necessarily 

 project more and thus produce a roughening of the skin, very per- 

 ceptible when the worms are handled. 



My experience of living Earthworms of the genus Megascolex is 

 limited to the examination of a specimen (as yet unidentified) from the 

 Seychelles. These worms are tar more lethargic in demeanour than 

 the extremely active Perichmtce, and it is quite possible that this 

 difference may be general. 



Another distinguishing character of the genus is the presence of a 

 pair of caeca ^ projecting forwards from the intestine in the xxvith 

 segment. The gizzard, moreover, lies in segments viii.-x. and 

 the septa are wanting which should divide those segments. No true 

 Perichceta is known in which the spermatheca have more than a 

 single diverticulum apiece ^ The clitellum never consists (with one 

 exception, P. fece) of more than three segments (xiv.-xvi.), and the 

 oviducal pore is generally, if not always, single and median \ 



Most naturalists who have described species of Perichceta have 

 mentioned the number of setse on the segments ; but a segment has 

 generally been selected at random, and frequently no mention has 

 been made of the particular segment chosen. Prof. Bourne points 

 out that it is desirable to count the setse upon more than one seg- 

 ment, and he selects segments v., ix., & xxv. ; he finds " that the 



' " Observations upon an American Species of Perichsta, and upon some other 

 Members of the Genus," P. Z. S. 1890, p. 52. 



- I refer later on in this paper (p. 165) to one exception to this rule. 



^ The second " diverticulum," in the form of a pear-shaped pouch, which 

 occurs in PerichcBta houlleti does not belong to the same category as the true 

 appendix of the spermatheca ; this I have pointed out elsewhere [Q. J. Micr. 

 Sci. vol. XXX. p. 462]. 



■* Fletcher has described and figured an Earthworm (" Notes on Australian 

 Earthworms: Part II." ; Proc. Linn. Soc. N. S. W. ser. 2, vol. i. pi. 13. fig. 6 



5 , and p. 962), Perichata qucenskmdica, wliich has the internal organization of 

 a true Perichata. but '■ interrupted " set^ and paired oviducal pores ; PerichcBta 

 darnlciensis, described on p. 966 of the same memoir, appears to be in every 

 respect a true PerichcBta, but has also paired oviducal pores. This matter, 

 however, requires looking into again, as llr. Fletcher suggests a slight doubt as 

 to whether the said apertm'es are really separate. 



