40 
THE VOYAGE OF H.M.S. CHALLENGER. 
The intestine arises from the posterior part of the stomach ; it is short and passes 
directly without any flexure to the right side, where the anus is situated. Thus the 
curvature of the digestive tract is lateral and to the right, and not neural. If it appear 
a little ventral this is in consequence of the great reduction of the pedal surface. It 
opens into a cloacal depression, like that of Clionopsis (PI. IV. fig. 10), where is also 
found the opening of the kidney. 
The Respiratory and Excretory Organs. — The situation and structure of the gills 
have been already described in three genera in the systematic portion of this Report. 
The primitive gill is the lateral one, which also is nearest to the auricle of the heart, this 
latter being posterior. For the rest the heart is shaped as in the Thecosomata. The 
arterial system is more easily followed than in these latter ; but it does not present any 
special or interesting disposition. 
The kidney, whose existence was suspected by Gegenbaur, 1 is an organ with thin 
walls, not very obvious, and difficult to demonstrate by dissection. It is made up, as in 
Clionopsis and Clione, of a flattened sac, situated between the visceral mass and the 
lateral gill, and opening anteriorly into the cloacal depression near the anus. 
The Generative Organs. — The genital gland (PI. IV. fig. 8, a) occupies the posterior 
part of the visceral cavity. It forms a compact mass, presenting lobes more or less 
distinctly separated. The genital duct (b) arises from the anterior part of the gland, a 
little ventrally ; it is rather thin at its origin, but dilates as it proceeds as far as the 
middle of its course. 
This duct, somewhat coiled, reaches the accessory genital glands, which are situated 
ventrally at the anterior end of the visceral mass ; among these may be distinguished a 
coiled muciparous gland (c), and a small albumen gland ( d ), situated on the back of the 
other and to some extent embedded in it. 
After these two glands the genital duct presents a receptaculum seminis (e) rather 
long and ovoid in shape ; then it opens on the right side of the cervical region behind the 
posterior margin of the fin of that side. At the genital aperture (f) commences a 
ciliated spermatic groove, parallel to the fin, and passing forwards in front of the anterior 
border of the fin to the orifice of the penis, which is situated on the anterior aspect of 
the right side of the foot. The penis, which is coiled up in a cavity of the head, is rather 
long, and has the same form as in the other Gymnosomata, such as Clione , 2 
The Nervous System. — The only information we possess regarding the nervous 
system of the Pneumonodermatidse is derived from the researches of Cuvier, 3 van Beneden, 4 
Souleyet, 5 and Gegenbaur, 6 and is based upon the study of the genus Pneumonoderma alone. 
1 Untersuchungen iiber Pteropoden und Heteropoden, p. 86. 2 Zool. Chall. Exp., part lviii. p. 47. 
3 Memoire sur l’Hyale et la Pneumoderme, Ann. Mus. Hist. Nat. Paris, t. iv. p. 225, pi. lix. B, fig. 9. 
4 Recherches anatomiques sur le Pneumodermon violaceum, d’Orb., Mem. Acad. Sci. Bruxelles, t. xi. p. 43, pi. i. fig. 2. 
6 Voyage de la Bonite, Zoologie, t. ii. p. 267, pi. xv. figs. 29-38. 
6 Untersuchungen fiber Pteropoden und Heteropoden, p. 97. 
