INSTINCTIVE HABITS. 325 



ledge whatever of those physical and chemical laws 

 to which it is adapted. The tendency to act in 

 a manner suited to those laws is a part of their 

 constitution. It exhibits one of the most striking 

 evidences that it is possible to conceive of over- 

 ruling foresight on the part of that Infinitely 

 Wise Being to whom all the laws of the material 

 universe are known, and from whose special in- 

 struction alone, creatures, without any design 

 arising from their own intelligence, act in the 

 strictest conformity to those laws, and so answer 

 the purposes for which they are called into 

 existence. 



The skeletons of fishes are formed either of 

 cartilage, as in the skate, or of bone, as in the 

 trout or perch. This circumstance has been 

 adopted by the illustrious naturalist Cuvier as 

 the basis of his classification. He has accordingly 

 divided fishes into two primary groups, the one 

 comprehending all the osseous fishes, the other 

 all the cartilaginous tribes. These two groups 

 admit of further subdivision with reference to 

 certain peculiarities in the fins and other parts. 

 It is, however, unnecessary minutely to describe 

 the details by which those subdivisions are dis- 

 tinguished. 



Y 3 



