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Show 172 ON WORMS OF THE GENUS PERICH.ETA. [Feb. 16, they fuse with the larger tube, and all these open by a common orifice. Traced in the reverse direction, one of the two smaller tubes was found to communicate with a separate lobe of the branched atrium. Whether this was or was not the case with the second of the two smaller tubes, I am not able to say. These facts are of interest in relation to the structure of the terminal portion of the male efferent apparatus in Perichceta ceylonensis, a species which I described some years ago. Perichceta ceylonensis differs from all other species of the genus in possessing two glandular bodies on each side in the xviiith segment. One of these is a lobed atrium like that of Perichceta in general, but with a straight instead of a curved muscular duct; the other is a tubular gland like the atria of Acanthodrilus. Unfortunately I have not been able to ascertain with which of these two glandular appendages the vasa deferentia communicate. It seems to me that in this Perichceta there is a commencing separation of each atrium into two halves which culminates in Perichceta ceylonensis. EXPLANATION OF THE PLATES. PLATE IX. Fig. 1. Perichceta morrisi. Nat. size. 2. Perichceta dyeri. Nat. size. 3. Perichceta sinensis. Nat. size. 4. Perichceta sumatrana (?). Nat. size. 5.v Genital segments of Perichceta sinensis. 2 > oviducal pore ; 3 > atrial pore; p, genital papilla. The segments are numbered, those of clitellum in roman numerals. 6, 7. Genital segments of Perichceta barbadensis, two varieties; letters as above. 8. Genital segments of Perichceta dyeri; letters as above. PLATE X. Fig. 1. Perichceta dyeri, a portion of intestine and dorsal vessel showing septal glands. D.V., dorsal vessel; Int., intestine; Spt., intersegmental septum ; gl., septal glands. 2. Perichceta sinensis, mulberry-shaped glands (p.g.) corresponding to papilla?. 3. Perichceta sinensis, a portion of contents of spermatheca in fresh condition. 4. Perichceta sinensis, a spermatheca drawn in the fresh condition. sp., spermatheca ; d., diverticulum. 5. Perichceta mauritiana. Spt., septum between segments xii./xiii.; Spt.', septum between segments xiii./xiv. ; r.o., receptacula ovorum; ov., ovary ; /., funnel of od., oviduct. 6. Perichceta mauritiana. N., nerve-cord ; v.d., vas deferens; ^..muscular part of atrium ; p.g., glands corresponding to papillae. 7, 8. Perichceta sinensis, vascular plexus from spermathecal appendix. |