858 EECORD OF CCJKRENT RESEARCHES RELATING TO 



in a large deep vessel with muscular walls, which soon ramifies on 

 the lower surface and on the thickness of the large gland, already 

 alluded to. From this network the efferent vessels take their origin, 

 the greater part of which reunite in a large trunk with muscular walls 

 which carries the blood to the renal organ : this is the deep afferent 

 vessel of the renal organ, peculiar to the Ampullarim. The other 

 vessels which originate from the large gland discharge themselves 

 successively into a superficial vessel of no great size, placed on the 

 posterior margin of the renal organ, and which is its superficial afferent 

 vessel, corresponding in all respects to the single afferent vessel of the 

 other Pectinibranchiata. Hence the blood which has traversed the 

 large gland in a true jiortal system is not, as M. Jourdan thinks, 

 mingled with the blood returning from the organs of respiration, to 

 be immediately poured into the heart, but it does not reach the latter 

 until after it has traversed the renal organ first and the respiratory 

 organs afterwards. 



From the anterior margin of the renal organ there originates, by 

 successive roots, an efferent vessel of the renal organ, which, after 

 having anastomosed with the afferent vessel of the same organ, con- 

 tinues forward on the right margin of the principal branchia, of 

 which it constitutes the afferent vessel. This vessel receives, in 

 passing, some affluents from the rectal sinus. 



On the left margin of the branchia, between the latter and the 

 lung, is a large trunk which terminates at the auricle, and which is 

 not simply, as M. Jourdan thinks, an efferent vessel of the branchia 

 and of the lung. This vessel contains, in fact, a series of fissure-like 

 orifices, which pour into it the blood from the branchia, and two series 

 of circular orifices, of which the upper part are the efferent orifices of 

 the pulmonary arch, and the lower are the afferent orifices of the floor 

 of the lung. On this floor, in fact, the vessels which originate from 

 these orifices, ramify in a network of which the efierent branches con- 

 verge into a large trunk, overlooked by M. Jourdan, and which, 

 collecting the blood of the whole of the floor of the lung, empties 

 itself directly into the auricle. 



From this results the fact, entirely exceptional in the Pectini- 

 branchiata, that the auricle receives two totally distinct afferent veins. 

 The one is branchial and pulmonary, the other exclusively pulmonary. 

 This is a remarkable peculiarity of the anatomy of the Ampullarice, 

 which is in connection with the double respiration of these animals, 

 and with the alternations in function of the double respiratory appa- 

 ratus. 



The afferent vessel of the branchia and the proper afferent vessel 

 of the hmg meet in front in such a manner as to form an anterior 

 arch. The intermediate trunk meets this arcade very obliquely and 

 imder a very sharp angle open to the left. There is thus formed 

 between the two vessels a valvular spur, which plays an important 

 part in several respects. When, during sojourn in the water, the 

 pulmonary respiration and circulation are suspended by the want of 

 air and the collapse of the lung, the blood of the proper afferent 

 vessel of the lung, being unable to traverse the pulmonary network, 



