184 MEMOIRS OF I'lIE NATIONAL ACADEMY OF SCIENCES. 



From the dorsal .side of tlic iimoiiiiiiatcs, near the origins of the inferior mandibular arteries. 

 arise arterioles which pass into the cerebral ganglia. From the ()osterior side of the innoiniiiiites 

 other small vessels pass into tlii' posterior portion of the hood. 



Finally, each innominate divides, one branch passing backward into the shell mustdes and 

 forming the anterior colmnellar artery, the oth(>r l)ran(h passing forward and downward along 

 tlie bases of the tentacles, foi'ming the pedal artery. Near the bas(> of the pedal ai'tery two 

 arterioles pass outward to the eye. Between these a large branch ai-ises from the pedal artery 

 which passes to the funnel, tiie infundibular artery. The remainder of the pedal artery, which 

 gives otif In-anches to tlie individual tentacles. Wili.ey has very conveniently named the tentacular 

 artery. The first of the branc'lies of the tentacular artei-y ))ass("s into tiie inferior labial lobe in 

 the female, and into Van dkk Hof:ven"s organ in the male. 



The origin of the genital and gonaducal arteries and thf artery <>f the pyriform sac has 

 already been mentioned. 



The genital artery passes from tlu' heart directly l)ack upon the gonad, in which it breaks 

 iij) into capillary brandies. 



The gonaducal artery passes to the right from the heart and is distril)uted to the walls of 

 the functional genital duct. 



The artery of the pyriform sac. or the non-functional genital duct, passes to the left from 

 the heart ar d extends along this organ. 



WiLLEY shows that l>oth the gonaducal artery and th(» artery of the pyriform sac give ofl' a 

 branch which passes into the perigonadial memlirane. and he says: ''This ajiparently trifling fact, 

 combined with the subsymm(>trical iclations of the gonaduct and the pear-shaped gland, may 

 indicate that the latter is the metamorphosed genital duct of the h^ft side, and not. as I believe 

 has been suggested, the morphological equivalent of an entire left genital apparatus." 



Almost immediately after its origin from the anterior side of the heart, the les.ser aorta 

 divides into two branches.' One. the pallial artery, runs straight forward in the median line of 

 the mantle and is distributed to the intestine, rectum, and mantle. The other, the counnon 

 septal arterv. runs almost straight backward and is distributed entirely to the septal portion of 

 the l)ody wall and tiie siphuncle. 



The pallial artery is inclosed by the pallio-visceral ligament. A few millimeters anterior to 

 the heart it gives otf a sliMider l)ranch (the intestinal artery), which runs ])ack in the membrane 

 uniting the two portions of the second loop of the intestine. Small aiterioles pass from either 

 side into the intestinal tissues. 



In front of the intestinal artery several small rectal arteries arise directly from the pallial 

 art(MT and pass to the walls of the rectuiu. 



At the point where the two walls of the mantle fold unite and the mantle becomes thin, a 

 pair of vessels arise from the pallial artery and pass outward to the I'ight and the left in the sub- 

 stance of the mantle. These arteries, discovered by Willey. were callt>d by him the branchio- 

 osphradial arteries, "since among their minor ramifications they send up lu'anches to the tips of 

 the branchia'. supplying tht> integument of the latter, and also a small l)ranch into each of the 

 osphradia." In the fcMuale the nidamental glands are supplitnl by branches of the branchio- 

 osphradial arteries. 1 retain the name " branchio-osphi-adial " for these arteries because, although 

 the osphradial character of the i)apilhe referred to is not yet well proven, there is still a consider- 

 able probability of it, and it do(\s not seem worth while to burden the literature of the subject 

 with a new name which might in time jirove more correct, but for the pres<Mit would be no more 

 intelligible or convenient. 



The pallial artery now passes forward nearly to the mantle edge. It here divides into a right 

 and a left liranch (the marginal pallial arteries), which run parallel to the edge of the mantle till 

 they unite dorsally with the pallio-nuchal branches of the dorsal aorta. In this way a remarkable 

 arterial circuit is formed, to which Willey has given the name "circulus pallialis." 



'The arteries dewriljed after this are represented in text-fij;. 11 



