ACEPHALA LAMELLIBRANCHIATA. 31 



convey the blood throughout the system, and another visible 

 elaborate apparatus to eliminate the vital element, that she 

 would stop in the midst of her career, and, instead of a set 

 of vessels to convey it back to the branchiae for oxygenation, 

 substitute and allow the stream of vitality to find its way 

 through a mixture of cavernous sinuosities, and percolate 

 amidst the ordures of the visceral contents to the mouths of 

 the branchio-cardiac vessels, to pass it to the respiratory me- 

 chanism to repair the usual exhaustions and adscititious impu- 

 rities of its passage. 



Neither of these opposite views can be verified in the living- 

 animal, and the examination of the dead one is equally unsa- 

 tisfactory, because uncovered sinuous canals may appear to 

 exist in the tissues ; but who can say that the excessively thin 

 walls may not have vanished by contraction attendant on the 

 peculiar mode of death, leaving only the sinuosities of their 

 sites ? 



The above remarks are confined to the circulation of the 

 blood. I fully admit that in many of the Mollusca, aquiferous 

 canals and pores exist in the tissues of the foot and its pedicle, 

 and other organs for the admission of water to assist in pro- 

 moting the tension of those organs in aid of locomotion ; but I 

 do not believe that the water enters the visceral regions except 

 by the mouth, unless in consequence of a rupture of the parti- 

 tion-membrane between the cavities of the foot and the abdo- 

 men ; it has been stated that the Lucinas are instances of the 

 water passing through the foot into that cavity. 



For these reasons we repudiate, as contrary to nature and 

 all analogy, the doctrine of even a qualified lacunose system 

 for the blood circulation ; that is, of its being sent by arteries 

 to all parts of the organism, and returned partly by walled 

 vessels, and partly by sinuous canals worked out of the paren- 

 chyme. 



And in the tribes of inferior organization to the Mollusca, 

 we consider, however imperfect the mechanism of the susten- 

 tation. and circulation may be, that both these functions are 

 distinct, and in no case confounded; we believe that nine- 

 tenths of the matter that has been advanced by authors on 



