PHYSIOLOGY OF THE INVERTEBRATE HEART. 13! 



3. The Diatocardic Prosobranchs. - -Nerves to the heart of the 

 diatocardic prosobranchs have been described by Lacaze-Duth- 

 iers (1859), Haller (1883), Bouvier (1889), and Illingworth 

 (1902). Lacaze-Duthiers describes in Haliotis four nerves from 

 the pleuro-visceral connectives and the visceral ganglion to the 

 pericardium. He calls these cardiac nerves, but he does not 

 trace them to the auricles or the ventricle. Haller finds that 

 the heart of Fissurella, Turbo and TrocJius is innervated from two 

 different ganglia. He traces nerves from the branchial ganglia 

 along the efferent gill sinuses to the auricles, while the ventricle 

 is innervated by a nerve from the visceral ganglion that reaches 

 the ventricle along the aorta. Bouvier describes similar nerves 

 to the auricles and the ventricle of Patella, Nerita and Helicina, 

 but he does not figure the course of the nerve from the visceral 

 ganglion to the ventricle nor does he state whether the nerve 

 enters the ventricle along the rectum or at the aortic end. Illing- 

 worth states that the cardiac nerves described by Haller and 

 Bouvier are also present in Lucapina. 



My own work was done on Lucapina crenulata and Haliotis 

 cracherodii. In Haliotis (PI. V., Fig. 7) two nerves (7 and 8) 

 can be followed from the visceral ganglion or from the pleuro- 

 visceral commissures close to the ganglion, to the renal organ 

 and the base of the auricles. The nerves were not traced on to 

 the auricular musculature, but I have physiological evidence 

 that motor nerves from the visceral ganglion supply the auricles 

 and it is probable that they reach the auricles in the trunk of the 

 nerves 7 and 8. The visceral ganglion also gives off two nerves 

 to the pericardium, one (9) passing to the dorsal, the other (10) 

 in the ventral wall. The latter nerve sends one or two branches 

 on to the aorta, but I did not succeed in tracing these branches on 

 to the ventricular musculature. It can be shown physiologically, 

 however, that motor nerves from the visceral ganglion enter the 

 ventricle at the aortic end, and it is probable that these nerve 

 fibers reach the organ in the ventral pericardial nerve. The in- 

 nervation of the ventricle of Haliotis is consequently the same as 

 that described by Haller for Fissurella, Turbo and TrocJius, a 

 nerve from the visceral ganglion entering the ventricle at the 

 aortic end. I did not succeed in tracing any nerves from the 



