NOMENVLAfU-RE. 145 



It is here assumed, that a heart exists in all animals, and 

 that the modifications which it exhibits, are best adapted for 

 the construction of the primary divisions. It was, how- 

 ever, well known to LINN.EUS himself, that the existence 

 of a heart in many vermes, had not been demonstrated, 

 and that its occurrence was not even probable. If he had 

 resolved to employ the heart as the basis of his classifica- 

 tion, lie ought to have formed his divisions from the cir- 

 cumstance of some animals having a heart, while others 

 have nothing analogous to that organ. But, even after 

 having made choice of its modifications, we still find him 

 departing from that unity of principle which alone is com- 

 patible with precision. The heart having two auricles and 

 two ventricles, distinguished one class sufficiently from the 

 other, in which one auricle and one ventricle only were 

 present. In the formation, however, of his third class, he 

 has recourse to a repetition of the term uniloculare, by which 

 it becomes obvious that it is merely a modification of his 

 second class. But it may be said, that this third class is 

 distinguished from the second by a negative character in- 

 auritum. It is obvious, however, that the characters uni- 

 auriium and inauritum, occupy a subordinate rank to uni- 

 loculare, and should mark orders, not classes. It is like- 

 wise unfortunate, that this character should be false in re- 

 ference to several of the tribes which it includes. There 

 is a new character introduced into the third class, which 

 shews very plainly the obstacles which presented them- 

 selves to the author in its formation. The circulating fluid 

 of the two first classes, he terms sanguis, that of the second 

 sanies. It appears, however, that this character is subor- 

 dinate to the one which should have formed an order, as it 

 depends not merely on the unilocular heart, but on the ab- 

 sence of an auricle. The coldness of the sanies is similar 

 to the coldness of the snnguis of the second claps, and it 



VOL. II. K 



