| OCR Text |
Show 1886.] LITTLE-KNOWN EARTHWORMS. 301 there are three or four pairs of genital papillae, one to each of corresponding number of segments following the 18th. There was, however, no indication of an additional median papilla on each of the segments as in P. horsti, nor does Perrier mention anything of the kind. The clitellum is not, as is so generally the case, restricted to three segments ; but, at least in one specimen, extended from segment 14 to 17 inclusive; on the 17th segment, however, it was only developed on the dorsal region of the body. The orifice of the oviducts occupies the usual position on the ventral median line of the 14th segmentl. The spermathecal orifices are between the 7th and 8th and Sth and 9th segments. The setae are continuous all round the body and are everywhere of uniform size. With regard to internal structure, there are one or two features ia which this species is peculiar. In the first place, the spermathecae are separated from each other by very stout mesenteries, which are also found between segments 8- 7, 7-6, 6-5 ; in front of the fifth segment the mesenteries are more or less indistinguishable, forming a mass of muscles which bind the pharynx to the parietes ; behind the 9th segment the mesenteries are comparatively thin and delicate. The gizzard is situated in the Sth segment, that which contains the anterior pair of spermathecae ; it does not, as is so commonly the case (e. g. in P. affinis) occupy two segments, the intermediate mesentery having disappeared. The spermathecae consist of an oval or sometimes cylindrical pouch communicating with the exterior by a narrow duct, to which is attached a short diverticulum of much the same shape as the pouch. The diverticulum appears never to lie in a different segment from the spermatheca. The ovaries and oviducts were very distinct, and appear to occupy the normal position. The vasa deferentia open on to the exterior in common with the duct of a compact prostate. The testes are to the number of two pairs and in the usual position. The oesophagus widens into the intestine at about the 20th segment; 1 The extension of the clitellum over four segments, combined with the regularity and uniform size of the setas, makes it difficult, in the absence of additional information, to distinguish this species from P. cceridea, E. P.; it is stated, however, that in P. ceerulea the female generative orifices are paired. Nevertheless this latter difference is not perhaps of very fundamental value; it must at any rate be discounted by m y own observations with regard to Megascolex (Ann. & Mag. Nat. Hist., Oct. 1883), where the female pore is sometimes single and sometimes double. Perichceta taitensis of Grube (Reise der Novara, Anneliden, p 35 pi. iv. fig. 2) is a very doubtful species, agreeing with P. horsti in having only two pairs of spermathecae situated in the 8th and 9th segments. It m ay possibly be identical with it. I may take this opportunity of remarking that several other species described by Grube (MB. Akad. Berlin, 18/7, p. 5o3) are in need of revision. Lumbricus kerguelarum appears to m e from his description to be undoubtedly referable to the genus Acanthodrilus, and perhaps to Lan-kester's species A. kerguelenensis; L. tongaensis is certainly not a Lumbricus, and perhaps belongs to the same genus as the last. |
