THE GASTROPODA 



individuals, during normal respiration, the ventricle beats not more 

 than one hundred times nor less than thirty times in a minute. 



XVII 



XVI 



XI 



VI 



Fio. 79. 



DvritpUosa, opened dorsally. I, stomach; II, liver; III, ventricle of heart ; IV, pericardium 

 laid open; V, pallial vein; VI, gill; VII, branchial vein; VIII, anus; IX, renal pore; X, 

 auricle ; XI, reno-pericardial orifice ; XII, posterior part of intestine (the anterior part is on the 

 left); XIII, kidney; XIV, accessory genital glands; XV, tentacle; XVI, central nervous 

 system ; XVII, hematic gland ; XVIII, salivary gland ; XIX, oesophagus. (After Hancock.) 



The mean frequency of the pulsations is sixty to the minute in 

 forms most easily observed, such as Pulmonates, Nudibranchs, 



