ANIMAL LIFE GENERATION. 355 



more or less circular units. This division we 

 shall subdivide in the following manner. 



1. Worms, represented by the annelids, or 

 the ringed earth-worm. 



2. Arthropods, or the joint-footed insects, 

 spiders, myriapods, Crustacea. 



3. Chordates, in whose body the notochord 

 or primal backbone appears (cartilaginous), 

 which begins to connect the articulation. Of 

 this class (or sub-tribe) there are several 

 less important divisions till the highest and 

 most important portion of the animal king- 

 dom is reached in 



THE VERTEBRATES. 



This is now classified as a division of the 

 Chordates, which in turn come under the 

 Segmentates, which in turn come under the 

 Metazoa, which again form one of the main 

 divisions of the animal world a position held 

 not very long since by the Vertebrates. This 

 may be taken as a sample of the present ten- 

 dency to revolutionize former classifications. 

 Still the conception of the Vertebrate and the 

 word also hold their place in science as well 

 as in literature. The term belongs to La- 

 marck (1797), though the conception existed 

 before him; in fact it has been traced back 

 to Aristotle, who, however, takes the blood 



