238 ANIMAL PEDIGREES 



see, Amphioxus has not yet, either in its develop- 

 ment, in its structure, or in its habits, been shown 

 to present characters that suggest, still less that 

 prove, the occurrence in it of general or extensive 

 degeneration. In a sense all the higher animals 

 are degenerate ; that is, they can be shown to 

 possess certain organs in a less highly developed 

 condition than their ancestors, or even in a rudi- 

 mentary state. Thus a crab as compared with a 

 lobster is degenerate in the matter of its tail, 

 a horse as compared with Hipparion in regard to 

 its outer toes ; but it is neither customary nor 

 advisable to speak of a crab as a degenerate animal 

 compared to a lobster ; to do so would be mislead- 

 ing. An animal should only be spoken of as 

 degenerate when the retrograde development is well 

 marked, and has affected not one or two organs 

 only, but the totality of its organisation. 



It is impossible to draw a sharp line in such 

 cases, and to limit precisely the use of the term 

 degeneration. It must be borne in mind that no 

 animal is at the top of the tree in all respects. 

 Man himself is primitive as regards the number of 

 his toes, and degenerate in respect to his ear 

 muscles ; and between two animals even of the 

 same group it may be impossible to decide which 

 of the two is to be called the higher and which the 

 lower form. Thus, to compare an oyster with a 

 mussel. The oyster is more primitive than the 

 mussel as regards the position of the ventricle of 

 the heart and its relations to the alimentary canal ; 

 but is more modified in having but a single 



