14 A MONOGRAPH OF THE 



In the Borididm there is generally a small pancreatic organ — a glandular sac — opening 

 into the intestine at its junction with the stomach. In B. tulerculata, this organ is situated at 

 the cardiac extremity of the gastric pouch. There is also a rudimentary pancreas in Tethys. 



Reproductive Organs. All the Nudibranchs are hermaphrodites, each individual being 

 furnished with male, female, and androgynous parts. These organs, taken together, are very 

 bulky, and occupy the greater portion of the abdominal cavity. They communicate with a 

 common vestibule, opening upon a nipple-like process on the right side of the body, and always 

 below the mantle, when it is present. 



The male intromittent organ is exserted in front ; behind it opens the vulva, and a little 

 above and between these two orifices is the vaginal opening, leading to the androgynous 

 apparatus. The penis is usually long, tapering, pointed and perforated, and the testis is 

 composed of a convoluted glandular tube, more or less voluminous, which, in some of the 

 Boridida, is rolled up into a dense mass, forming a compact gland-like organ. One end of 

 this tube is connected with the intromittent organ, the other with the oviduct.* 



The ovary is of considerable magnitude, and occupies the posterior portion of the 

 abdomen. In the Boridida and Tritoniadm, it is spread over the upper surface of the liver ; 

 in the Eolididse, it is a bulky, lobulated organ, filling up the space held by the liver in the 

 other members of the order. The oviduct, as it leaves the ovary, is very slender ; it soon 

 widens and is more' or less convoluted, and, after joining the testis, and receiving a duct from 

 the androgynous apparatus, sinks into a large mucus-gland, composed of a convoluted tube, 

 that opens into the vulva. This gland secretes the mucus, which, on reaching the surrounding 

 water, is transformed into the transparent gelatinous substance in which the eggs of the 

 Nudibranchs are always imbedded. 



The androgynous apparatus consists of the vagina, or copulatory channel, which unites 

 with the oviduct, and has seated upon it one or two sperm athecse : in the Doridida always 

 two; in the Tritoniadce and Eolididce generally only one. The connexion of the androgynous 

 with the female parts is somewhat modified in Tritonia and Tethys. 



Such is the predominant arrangement of these organs. There are, however, occasional 

 modifications. Thus, in Boris Johnstoni; and Boris tomentosa (of Verany) the male organs 

 have added to them a stiletto, which lies within a sac in front of the penis : this sac can be 

 everted, and when so, the stiletto projects from the apex of a long penis-like organ. This, 

 like the dart of Helix, is probably for a stimulating purpose during, or previously to, coitus. 

 But the Hermceince present the most important deviations. In this sub-family the male and 

 female orifices are divided from that of the androgynous apparatus. The two former openings 

 are placed close together at the base of the right tentacle, and when these parts are fully 

 retracted, only one opening is visible externally. The copulatory orifice is removed to some 



* Having completed our investigation of the anatomy of the various genera, we think it only 

 right to state that several facts have been observed, particularly in the anatomy of the Polycerina, 

 which would seem to favour Her Heinrich Meckel's views as to the compound nature of the ovary of 

 these animals. "When in season, it is distinctly composed of two parts, one containing ova, the other 

 spermatozoa, and these latter have been found lying in parallel order, and apparently in an incipient 

 state. The oviduct is, however, simple, and does not hold within it a vas deferens, as supposed by the 

 same high authority. Therefore, if the so-named ovary be really composed of ovary and testis, the 

 oviduct must be equally oviduct and vas deferens. 



