450 MORPHOLOGY. 



Professor Hackel in his '^ Generelle Morphologie " and 

 in other works, has recently brought his great knowledge 

 and abilities to bear on what he calls phylogeny, or the 

 lines of descent of all organic beings. In drawing up the 

 several series he trusts chiefly to embryological characters, 

 but receives aid from homologous and rudimentary organs, 

 as well as from the successive periods at which the various 

 forms of life are believed to have first appeared 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, in- 

 dependently of their habits of life, resemble each other in 

 the general plan of their organization. This resemblance 

 is often expressed by the term "unity of type;" or by say- 

 ing 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 Morphology. 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 poi'jDoise, 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-eat- 

 ing, bandicoots — and those of some other Australian mar- 

 supials — should all be constructed on the same extraor- 

 dinary 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 

 animals are used for as widely different purposes as it is 

 possible to conceive. The case is rendered all the more. 



