DEGENERATION. 57 



I have already mentioned as best explained by the 

 supposition that they are the descendants of far 

 larger and more fully-organized animals provided 

 with locomotive appendages or limbs : they have 

 dwindled and degenerated to their present minute 

 size and curiously suggestive structure. 



Besides these there are other very numerous cases 

 of animal structure which can best be explained by 

 the hypothesis of degeneration. A discussion of these, 

 and a due exposition of the application of the hypo- 

 thesis of degeneration to the various groups just cited, 

 would involve a complete treatise on comparative 

 anatomy and embryology, and lead far beyond the 

 limitations of this little volume. 



All that has been, thus far, here said on the subject 

 of Degeneration is so much zoological specialism, 

 and may appear but a narrow restriction of the dis- 

 cussion to those who are not zoologists. Though w^e 

 may establish the hypothesis most satisfactorily by 

 the study of animal organization and development, it 

 is abundantly clear that degenerative evolution is by 

 no means limited in its application to the field of 

 zoology. It clearly offers an explanation of many 

 vegetable phenomena, and is already admitted by 



