PHYSIOLOGY OF THE INVERTEBRATE HEART. 135 



branch (3) communicates with the ganglion on the ventriculo- 

 aortic junction (8). The large visceral ganglion on the right side 

 also gives rise to several nerves, one of which (5) can be followed 

 with the unaided eye through its course in the pericardium till it 

 enters the ganglion on the ventriculo-aortic junction. Branches 

 from nerve 7 enter the renal organ. Nerve 4 enters the repro- 

 ductive gland and the liver. Apart from nerve 5, which plainly 

 enters the ventricular ganglion and is therefore, a cardiac nerve, 

 there are several branches from nerves 4 and 6 that ramify in the 

 pericardium. Whether any of these branches enter the auricle 

 at its base I am unable to make out. 



The ganglion on the ventriculo-aortic junction is large enough 

 to be seen by the naked eye, and by the aid of a dissecting lens 

 nerves can be traced from the ganglion for some distance on the 

 ventricle (9). 



There is no evidence of nerve-fibers passing from the branchial 

 ganglion to the auricle. Either end of the heart is supplied with 

 nerves from the visceral ganglia, and this is born out by the 

 physiological experiments. The commissure between the two 

 visceral ganglia is partly ganglionic and pigmented like the vis- 

 ceral ganglia themselves. 



5. TJie Tectibranchs. In his description of the nervous system 

 of Pleurobranchus Lacaze-Duthiers (1857) does not come to any 

 definite conclusion regarding the innervation of the heart. " Sur 

 1'oreillette, on trouve des filets nerveux evidents, mais qu'il m'a 

 ete impossible, vu leur delicatesse, de les suire jusqu'a leur ori- 

 gin " (p. 285). But he believes that the auricular nerve makes 

 connection with the right peripheral nerve from the visceral 

 ganglion. This nerve is called by him the genital nerve. Dogiel 

 (1877) describes in Aplysia a nerve to the auricle from the left and 

 posterior side of the visceral ganglion. Vayssiere (1879) has fig- 

 ured and described the nervous system of Gasteropteron, Doridium, 

 Philenc, Scaphander and Bulla, all of which belong to the family 

 Bullididae. Of the visceral organs he describes the innervation 

 of the oesophagus, the stomach and the reproductive organs, but 

 he makes no mention of the innervation of the heart. Ransom 

 (1884) has shown that the left side of the visceral ganglion of Aply- 

 sia gives origin to two instead of one nerve as figured by Dogiel. 



