THE GASTROPODA 97 
gland, and in the Fissurellidae there is a longish glandular caecum 
in the same position, which opens near the anus and lies alongside 
the rectum as far as the point where the latter traverses the ven- 
tricle. Asa rule, the anus opens on the right side of the body (on 
the left side in sinistral forms) and more or less in front. But in 
those forms in which the coiling of the visceral sac is diminished or 
lost, this flexure of the digestive canal seems to be effaced and the 
anus lies at the posterior end of the body. This disposition is rare 
1 a8 
3 
L : 
Ws 
AAC 
4, Lg 
Fic. 78. 
Tanganyicia rufilosa, dorsal view, with the mantle laid open. a, anus; b.p, brood-pouch ; 
b.p.o, orifice of brood-pouch ; ce.g, cerebral ganglion ; c7.s, crystalline style; f, foot; g, gill; h, 
heart ; in, origin of the intestine or pyloric orifice of the stomach ; m, mouth ; od, oviduct; oe, 
termination of the oesophagus, or cardiac orifice of the stomach ; 0.0, oviducal orifice ; os, 
Osphradium ; pa, mantle; st, stomach ; s.i.g, supra-intestinal ganglion. (After Moore.) 
in the Streptoneura, but may be seen in Cypraea and Pterotrachea. 
It is, on the contrary, common in the Euthyneura, occurring in 
Doridium, Runcina, Aplysia (Fig. 154), the Doridomorpha (Fig. 79, 
VIII), Janus, Alderia, Limapontia, Testacella, the Oncidiidae (Fig. 59), 
and the Vaginulidae (Fig. 87). 
2. The Circulatory System.—The blood is generally a colourless 
liquid containing amoebocytes. It is red in the genus Planorbis 
(with the exception of P. albus), in which haemoglobin is diffused 
in the plasma. The muscles of the buccal mass are impregnated 
7 
