MORPHOLOGY 241 



peared in our geological formations. He has thus boldly 

 made a great beginning, and shows us how classification 

 will in the future be treated. 



Morphology 



We have seen that the members of the same class, 

 independently of their habits of life, resemble each other 

 in the general plan of their organization. This resem- 

 blance is often expressed by the term "unity of type"; 

 or by saying that the several parts and organs in the 

 different species of the class are homologous. The whole 

 subject is included under the general term of Morphol- 

 ogy. This is one of the most interesting departments of 

 natural history, and may almost be said to be its very 

 soul. What can be more curious than that the hand of 

 a man, formed for grasping, that of a mole for digging, 

 the leg of the horse, the paddle of the porpoise, and 

 the wing of the bat, should all be constructed on the 

 same pattern, and should include similar bones, in 

 the same relative positions? How curious it is, to give a 

 subordinate though striking instance, that the hind feet 

 of the kangaroo, which are so well fitted for bounding 

 over the open plains — those of the climbing, leaf eating 

 koala, equally well fitted for grasping the branches of 

 trees — those of the ground-dwelling, insect or root eating, 

 bandicoots — and those of some other Australian mar- 

 supials — should all be constructed on the same extraordi- 

 nary type, namely, with the bones of the second and 

 third digits extremely slender and enveloped within the 

 same skin, so that they appear like a single toe furnished 

 with two claws. Notwithstanding this similarity of pat- 

 tern, it is obvious that the hind feet of these several 



