56 DUBLIN NATURAL HISTORY SOCIETY. 



it attain the size of a large swan-drop, being more than a quarter of an 

 inch ia 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 opportunities 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 coecum 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 thns the male element to the female. It seems 

 homologous with the duct connecting the sperm-sac and ovary in 

 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 mul- 

 tifid vesicles. The dart-sac is a pyriform vesicle, bearing 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 m length, and in diameter a little above a quarter at its bore or 

 fundus, and is provided with very dense and apparently muscular walls, 

 which are pierced on the left, close to the external opening, by the 

 termination of the vagina ; it communicates with the generative cloaca 

 by a small circular outlet, which is guarded by two delicately con- 

 structed 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 un- 

 likely that they may direct the penis in entering the vagina, and so 

 prevent the possibility of its being lacerated by any existing rem- 

 nant of the dart ; while, on the other hand, by opening in a valve-like 

 manner externally, they thus ofi'er 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 tubular, being connected at the base 

 with a small follicle, situated between the layers of the dart-sac. The 

 stilette appears to be the secretion of this papilla ; it is perfectly trans- 

 parent, about a quarter of an inch long, tapering from base to apex, it 

 is tetrahedral in foim, the sides being trenchant ; a transverse section 

 appears like a square, upon each of whose external sides an equilateral 

 triangle had been constructed ; it is perforated throughout, and at its 

 papillary extremity is funnel-shaped, the lips also being slightly everted. 



