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Show 64 MR. F. E. BEDDARD ON [Feb. 4, setae and the genital papillae ; and it is precisely these characters which lead m e to identify the present species, at least provisionally, with Perichceta biseriatis. The prostomium is small and does not divide the circumoral segment. The setce form a continuous row round each segment; on the ventral side a single pair, one on either side of the median line, are very much enlarged, being three or four times as large as the rest. On the anterior segments of the body two or three setae on each side are thus enlarged; posteriorly there is only a single pair of these setae. The clitellum occupies segments 14-16 inclusive and is developed all round the body. There are no setce on the clitellum l. The male generative pores are upon segment 18. The five succeeding segments each have a pair of genital papillce, which are placed in positions exactly corresponding with the male pores some distance on either side of the median line ; these papillae as well as the male pores are situated just in front of the ring of setas (Plate V. fig. 4). The oviducal pore is single and median upon the 14th segment. No spermathecal pores could be detected. Dorsal pores are present, but I am not able to state at which segment they commence. Concerning the internal anatomy I am not able to say much, as none of the specimens examined by me were in a sufficiently good state of preservation for section-cutting. The nephridia show the usual characters which are found in the genus Perichceta; they present a series of minute tufts attached to the body-wall; in some of the anterior segments they form immense masses completely occupying the cavity of the segment. There are only three mesenteries which are specially thickened ; these lie between segments 6-7, 7-8, 8-9 ; of these three mesenteries the last two are considerably thicker than the first. The gizzard lies behind the last thick mesentery and occupies at least two segments. The most remarkable fact about this species is that there are apparently no spermathecce. I have only been able to examine two specimens, and there was not the slightest indication of spermathecae in either of these. I cannot of course state positively that these structures are absent, which seems unlikely seeing that in all other species of Perichceta they are present; but the fact remains that they were undoubtedly absent in two examples, the only complete examples which I possess 2. 1 The presence or absence of setae on the clitellum is characteristic of a given species and should always be carefully noted. It serves, for example, to distinguish P. indica (where they are absent) from P. affinis (where they'are present). 2 Since writing the above I have received Eosa's paper (27) in which he refers to the absence of spermatheca in Lumbricus eiseni and Allolobophora constricta, besides Crioclrihis. |