TETHYS CERVINA BALL AND SIMPSON 53 



receives the distal end of the left pleuro- visceral connective. From 

 its posterior portion it gives origin to the following four nerves. 



1. From near the posterior median line arises a slender 

 nerve (PI. X, fig. 42, /. v. /), which immediately bifurcates to the 

 Vesicle of Swammerdam, or spermatotheca, and its duct, a slender 

 branch being also continued to the adjacent peritoneum. 



2. A large nerve (PI. VIII, fig. 35, /. v. 2), given off from the 

 posterior right side of the ganglion, passes obliquely backward 

 to the right, crossing the large hermaphroditic duct midway of 

 its length, to the posterior end of the body. It gives off a number 

 of slender branches to the dorsal peritoneum, and a larger one, 

 20,, to the liver, separating from the main nerve near its origin, 

 but continued with it in a common epineural sheath for some 

 distance. A little beyond the middle of its course the second nerve 

 gives off a moderately strong recurrent branch to the right, 20, 

 and then passes straight backward, 2b, bifurcating to the anal 

 portion of the intestine, and to the siphon. From the recurrent 

 nerve, 2c, a long, posterior branch, 2d, is given off, which is dis- 

 tributed to the peritoneum in the median posterior region near 

 the rectum ; the main nerve, curving forward, sends one or two 

 very delicate branches to the peritoneum, a stronger one, 2e, to 

 the posterior face of the Organ of Bohadsch, passes beneath the 

 right margin of the latter gland, and forms an anastomosis with 

 the terminal branch of the third pedal nerve, ^e, which, it will be 

 remembered, sends a branch to the anterior face of the Organ of 

 Bohadsch, and one uniting with the vulvar nerve from the right 

 parietal ganglion. By this arrangement the hypobranchial gland 

 receives its nerve supply not only from the right pedal ganglion, 

 but also from the left visceral one as well. It would be an inter- 

 esting physiological problem to determine the relative influence 

 of these two nerves with such different origins upon the secretory 

 activity of the gland. Mazzarelli ('90) has made a comparative 

 study of the morphology of the gland of Bohadsch in a number 

 of Aplysiidae, and has represented diagramatically the inner- 

 vation in seven species. In all of these the nerve supply is found 

 to be from the right pedal ganglion, but in none of them is any 

 mention made of such relations as are here described for the two 

 Brazilian species. In figs. 36 and 37 of Plate IX I have repro- 

 duced Mazzarelli's figures 17 and 19 of Tav. I for Tethys punctata 



