i 3 6 



THE GASTROPODA 



between the foot and anus, in front of the pallial cavity, e.g. 

 Helix, Bithynia, Fermetus, the Eachiglossa, and nearly all the marine 

 Gastropoda, including the "Pteropoda," Heteropoda, and Nudi- 



FIG. 116. 



Larvae of Eolls (Galvina) exigva. A, on the second 

 day, left-side view. I, radula ; II, foot ; III, otocyst ; 

 IV, operculum ; V, shell. B, on the third day, after 

 the loss of the shell, dorsal aspect. I, eye ; II, left 

 liver lobe ; III, foot ; IV, anus ; V, octocyst ; VI, 

 radula. (After Schultze.) 



branchia. This sinus is displaced, together with the pallial aper- 

 ture, along the right side towards the neck (Fig. 114, II), and 

 finally is partly contained in the pallial cavity. In the Basom- 

 matophora there is a velar dorsal sinus, and in the Stylommatophora, 



tuo< 



Helix aspersa, embryo of the tenth day, right-side view, coq, shell ; o.ca.c, external opening 

 of the cerebral cavity ; p, foot; pa, mantle; po, contractile vesicle or podocyst ; te", the true 

 tentacles ; te'", labial palp ; vit, vitellus. 



Arion, Limax, Claitsilia, Helix, etc., but not in Succinea, there is a 

 caudal vesicle, known as the pedal sinus or podocyst (Fig. 117, po). 

 The larval kidneys are paired and generally symmetrical organs 

 situated at the anterior end of the body, immediately behind the 

 velum or apical area. In the marine Streptoneura they are caducous 

 ectodermic projections, in which the products of excretion are 



