148 A. J. CARLSON. 



auricles on to the systemic ventricle. The ganglion at the base 

 of the gill measures I mm. in diameter in the largest specimens 

 and the ganglia on the gill ventricle and the auricle are only one 

 third as large, so that it is difficult to locate them by dissection, 

 especially as they are imbedded in the connective tissue that en- 

 velops these organs. From the gill ganglion a small branch 

 passes to the retractor muscle of the gill (8). In the male a 

 branch from the left visceral nerve innervates the penis (5). At 

 the level where the branches are given off to the ink gland (4) 

 commissural fibers extend across from one visceral nerve to the 

 other. This commissure would correspond to that described by 

 Cheron for the decapods. If branches are given off to the sys- 

 temic ventricle by the visceral nerves at this point as physiolog- 

 ical experiments indicate, and as Cheron found to be the case, 

 the systemic heart of Loligo has a double nervous supply, as 

 nerves unquestionably pass to the auricles along with the nerve 

 or nerves to the ganglia on the gill ventricles. Cheron figures 

 the ganglia which supply the nerves to the gill ventricles as situ- 

 ated on the trunks of the visceral nerves, and not on the ven- 

 tricles themselves, as I found to be the case in Loligo. 



The dissection of the smaller branches of the nerves in Loligo 

 is very difficult, because the nerves, the connective tissue and the 

 muscular tissue have in life very nearly the same color and trans- 

 parancy ; and in addition, minute arteries, which are hardly dis- 

 tinguishable from the nerves, run in the larger nerve trunks and 

 ramify with the smaller nerve branches. 



The specimens of Ominastrephes illcccbrosa obtained at Woods 

 Holl are more than twice the size of Loligo. The species of 

 Ommastrephes on the coast of California (O. calif arnica) attains a 

 length of from 3 to 3^ feet, but the only specimen of this large 

 species at my disposal was so badly preserved that the finer 

 branches of the nerves could not be told apart from the smaller 

 arteries. The main course of the visceral nerves in Ommastrephes 

 (Fig. 21) is the same as in Loligo. The commissure (w.) between 

 the two visceral nerves a little anterior to their lateral divergence 

 from the vena cava to enter the gills, is very distinct. The com- 

 missure gives rise to a nerve (2) which follows the vena cava in 

 a posterior direction to enter the ventricle. The nerve divides 



