PHYSIOLOGY OF THE INVERTEBRATE HEART. 133 



( 1 882) and Bouvier ( 1 889). Haller worked on Murc.v truncuhts. 

 In this mollusc there are three visceral ganglia. From the mid- 

 dle and largest ganglion a nerve passes along the aorta to the 

 ventricle, while the auricle is innervated from the nerve plexus 

 in the efferent gill sinus in the manner described by the same 

 author for Fissurella. Bouvier worked on several genera but he 

 describes the innervation of the heart particularly in Cyclophorus 

 tigrinus and Triton variegatinn. In Cydophoms he describes a 

 nerve to the ventricle only. "A gauche du ganglion (visceral), 

 la commissure viscerale donne naissance a un gros nerf cardiaque 

 qui suit un instant 1'aorte anterieure et penetre ensuite dans le 

 ventricle. On le voit tres bien entrer dans 1'organe sur la prep- 

 aration que j'ai conservie, et je pense qu'il n'est pas un type 

 plus commode pour 1'etude de 1'innervation du coeur" (p. 77). 

 In Triton there are two visceral ganglia connected by a commis- 

 sure. This commissure gives rise to three small nerves, one of 

 which passes to the branchial vein, another to the auricle, and 

 the third to the ventricle. This last nerve is given off by the 

 commissure close to the right visceral ganglion. It runs for 

 some distance in the pericardium and enters the ventricle at the 

 aortic end. 



My own work was done on Natica lezvissii and Sycotypus 

 caualicnlatns. In Natica (Fig. p) the right pleuro-visceral com- 

 missure is much stouter than the left. It enters the large bran- 

 chial ganglion on the left side, which gives rise to four nerves, 

 namely a comparatively large nerve to the osphradium and gill 

 (3), a smaller one to the floor of the pallial cavity (2), a some- 

 what larger branch to the gill (4), and finally a small branch to 

 the left visceral ganglion (5). On the course of this last nerve 

 is a small ganglion (7) which sends a tiny nerve to the ventral 

 wall of the pericardium (6). The two visceral ganglia are con- 

 nected by a commissure. The right ganglion is much larger 

 than the left. From the former two and sometimes three nerves 

 take their origin, the largest of which divides immediately after 

 leaving the ganglion, the main branch passing to the reproduc- 

 tive glands and the viscera (8), the smaller branch turning for- 

 ward and laterally into the ventral wall of the pericardium (9). 

 Branches from the two pericardial nerves (6 and 9) can be fol- 



