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Show 1892.] OF T H E G E N U S P E R I C H C E T A . 159 sketch does not show the prismatic colours, which were very evident. The hinder part of the body is extremely transparent and of a pale brown colour ; the blood-vessels and the paired septal glands were quite clearly visible through the thin integument. The last dozen segments or so are yellow-coloured; beyond the clitellum, which is grey, is a patch of yellow due to the prostate. The activity of this species is quite on a par with that of other Perichaetes, and it possesses the same power of everting the buccal cavity that I have referred to in the case of Perichceta indica 1 and the other species described in the present paper. M. Vaillant has also figured the same protrusion of the buccal cavity in Perichceta posthuma. In Perichceta sinensis the length of the fully everted buccal cavity was quite equal to that of the first three segments of the body. The length of the species is 126 mm., the circumference at the viiith segment 10 m m. The individual with the above measurements had 104 segments. The clitellum, as is occasionally the case, does not coincide exactly with the limits of the three segments (xiv.-xvi.) of which it is composed ; it begins after the furrow separating segments xiii./xiv., and ends before the intersegmental groove xvi./xvii. I could discover no setae upon it. The oviducal pore is single and median upon segment xiv. The atrial pores lie upon segment xviii. Genital papillce.-There are two large sucker-like papillae of circular outline lying between segments xviii./xix. ; each is placed a little to the inside of (and of course below) the atrial pore of its own side. The spermathecal orifices were not visible. As to the internal anatomy, this species shows the usual characters peculiar to the genus Perichceta. There are a pair of cceca in the usual position. There are four pairs of spermathecce lying in segments vi., vii., viii., and ix. In several individuals which I dissected the proportions between the pouch and its single diverticulum, as well as the shape of the diverticulum, varied. The normal condition appears to be for the diverticulum to be quite as long as the pouch ; like the pouch it consists of a distal sac where the spermatozoa are retained and a narrowed duct. The pouch itself contained no spermatozoa, only a quantity of material presenting the appearance shown in the accompanying drawing (Plate X . fig. 3 ) ; it is of a fluid consistency and contains minute granules as well as spherical bodies; the drawing, I should say, represents the contents of the pouch of a living worm. The diverticulum frequently shows a beaded appearance represented in fig. 4 ; in one case the upper end of the diverticulum was divided by constrictions into seven spherical chambers full of sperm; quite as often the diverticulum was tubular and of equal calibre throughout, except of course the proximal end, which is always narrower. My investigations upon the living worm, which I had 1 P. Z. S. lac. cit. |