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Show 1890.] WORMS O F T H E G E N U S PERICHCETA. 67 The spermathecce, 4 pairs, present nothing remarkable in their structure ; each is a small pear-shaped pouch with a single small stalked diverticulum. The sperm-sacs have a somewhat peculiar structure which is illustrated in fig. 10. In segments 11 and 12 are a pair of oval sacs; those of each side of the body are connected with each other, but there is no contact between the sacs of the right and left sides ventrally ; from each of the oval sacs is a small projecting tubelike outgrowth (tr, Plate V. fig. 10), which in the dissected worm appeared to be broken off at its extremity. 1 am inclined therefore to suppose that there is a connection above the intestine between the two sperm-sacs of each segment by means of these outgrowths ; if so, there is a striking resemblance in this particular between Perichceta vaillanti and Dichogaster, in which worm I have figured and described (10) an almost identical arrangement. The ovaries are in segment 13, attached to the anterior mesentery of this segment. The oviducts are perfectly normal. The atrium is again rather unusual in its structure ; as a general rule that portion of it which lies nearest to the external orifice has thickened muscular walls and is curved upon itself like a horseshoe ; its calibre gradually increases towards the external orifice. In Perichceta vaillanti the terminal portion of the atrium abruptly widens to form an oval, thick-walled sac, as in P. indica (Horst, 16), into which the thin tube-like proximal part of the atrium opens. The only species with which the present could be confounded is P. modigliani (Rosa, 25) ; but it differs from that species in having no thick mesenteries and apparently in the structure of the sperm-sacs. There is no knowing whetber P. vaillanti is the same as P. Juliana (Perrier, 19) : the only fact known about the latter species is that it has four pairs of spermatheca?. List of Memoirs cited. 1. BAIRD, W.-Description of a new Species of Earthworm (Megascolex diffiringens), found in North Wales. P. Z. S. 1869, p. 40. 2. B E D D A R D , F. E . - O n the Anatomy and Histology of Pleuro-chceta moseleyi. Trans. Roy. Soc. Edinb. vol. xxx. (1883), p. 481. 3. B E D D A R D , F. E . - O n the Anatomy and Systematic Position of a Gigantic Earthworm (Microchceta rappi), from the Cape Colony. Trans. Zool. Soc. vol. xii. pt. 3 (1886), p. 63. 4. B E D D A R D , F. E . - O n the genus Megascolex of Templeton. Ann. & Mag. Nat. Hist. M a y 1884, p. 398. 5. B E D D A R D , F. E.-Descriptions of some new or little-known Earthworms, &c. P. Z. S. 1886, p. 298. 6. B E D D A R D , F. E.-Observations on the Structure and Characters of certain new or little-known Earthworms. Proc. Roy. Soc. Edinb. vol. xiv. p. 156. 5* |