422 MORPHOLOGY. 



classification. We can understand why we value certain 

 resemblances far more than others ; why we use rudiment- 

 ary and useless organs, or others of trifling physiological 

 importance ; why, in finding the relations between one 

 group and another, we summarily reject analogical or 

 adaptive characters, and yet use these same characters 

 within the limits of the same group. We can clearly see 

 how it is that all living and extinct forms can be grouped 

 together within a few great classes ; and how the several 

 members of each class are connected together by the most 

 complex and radiating lines of affinities. We shall never, 

 probably, disentangle the inextricable web of the affinities 

 between the members of any one class ; but when we have a 

 distinct object in view, and do not look to some unknown 

 plan of creation, we may hope to make sure but slow 

 progress. 



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 curi- 

 ous 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 



