268 LAWSON^ ON HELIX ASPERSA AM) HOUTENSIS. 



seminal contents, I have often found it attain the size of a 

 large swan-drop, being more than a quarter of an inch in 

 diameter; whilst in specimens examined some time after the 

 performance of the sexual function, it has rarely exceeded the 

 bulk of a grain of sparrow-shot. I have had many oppor- 

 tunities of observing the nature of the contained zoosperms, ■ 

 yet I have never succeeded in seeing them isolated ; they 

 were invariably in enclosed bundles or spermatophora. The 

 caecum is an appendage whose function, so far as I am aware, 

 has not yet been investigated. It is a duct, springing from 

 the copulative tube, at about a quarter of an inch from its 

 union with the uterus. It measures three inches in length, 

 is of slightly greater calibre than the tube, and terminates, 

 by a blind extremity, at the point of junction of the uterus 

 and albumen-gland. It is closely attached to the sinus before 

 described, and, to a superficial observer, would seem to convey 

 thus the male element to the female. It seems homologous 

 with the duct connecting the sperm-sac and ovary iu Doris 

 and Eolis, which Messrs. Alder and Handcock have described 

 in their anatomy of the Nudibranchs. 



The appendicular group comprises the dart-sac, dart, and 

 multified vesicles. The dart- sac is a pyriform vesicle, bear- 

 ing in miniature a decided resemblance to the human uterus ; 

 it is situated at the anterior extremity of the animal, to the 

 right of the testes and penis, and is quite superficial, being 

 covered only by the outer integument and loose fibrous tissue 

 which involve the other organs. It is about half an inch in 

 length, and in diameter a little above a quarter at its base or 

 fundus, and is provided with very dense and apparently mus- 

 cular walls, which are pierced on the left, close to the ex- 

 ternal opening, by the termination of the vagina ; it com- 

 municates with the generative cloaca by a small, circular 

 outlet, which is guarded by two delicately constructed lips. 

 These may be traced from their point of union on the right 

 side of the orifice, passing round and approximating on the 

 left, where they leave a small portion unprotected. I would 

 be cautious in hazarding an opinion upon their function, but it 

 seems to me not unlikely that they may direct the penis in 

 entering the vagina, and so prevent the possibiUty of its being 

 lacerated by any existing remnant of the dart ; while, on the 

 other hand, by opening in a valve-like manner externally, 

 they thus offer no obstruction to the exsertion of the latter. 

 Springing from the fundus of the sac is observed a fleshy, 

 conical projection, armed at its free end with a calcareous 

 spicule — the dart or stilette. This projection, or papilla, is 

 about one eighth of an inch in length, and is distinctly tubu- 



