i 



LECTURE V. 207 



from the dorsal vessel in these animals, 

 says, they have not one aorta or distri- 

 butive trunk, but manv aortse. Professor 

 Cuvier, in his account of the organs for 

 the distribution of nourishment in the class 

 of vermes, principally appeals to the evi- 

 dence of what may be seen in the areni- 

 cola, or lumbricus marinus of Linneus. Sir 

 Everard Home, being particularly desirous 

 of examining the circulation in this ani- 

 mal, on account of its having external 

 branchiae, sent for Mr. Clift to the coast of 

 Sussex for this purpose ; and their conjoint 

 observations on the vessels and circulation 

 in this and other vermes, are printed in the 

 Philosophical Transactions for 1816. 



That Mr. Hunter was as well acquainted 

 with the circulation in animals of the worm 

 kind, as any of his successors, is, I think, 

 evident from his writings. He says, " they 

 have the most simple kind of circulation, 

 which is, when the blood, propelled by the 

 heart, becomes aerated in its circulating 

 passage." He also says, the motion of the 

 blood is a kind of undulation; which phrase, 



