32 PROFESSOR A. M, MARSHALL. 



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 rudimentary 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 misleading. 

 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 adductor muscle ; and almost certainly 

 degenerate in being devoid of a foot. 



Care must also be taken to avoid speaking of an animal as de- 

 generate in regard to a particular organ merely because that organ is 

 less fully developed than in allied animals. An organ is not degenerate 

 unless its present possessor has it in a less perfect condition than its 

 ancestors had. 



A man is not degenerate in the matter of the length of his neck as 

 compared with a giraffe, nor as compared with an elephant in respect 

 of the size of his front teeth, for neither elephant nor giraffe enters 

 into the pedigree of man. A man, is, however, degenerate, whoever 

 his ancestors may have been, in regard to his ear muscles ; for he 

 possesses these in a rudimentary and functionless condition, which can 

 only be explained by descent from some better equipped progenitor. 



Closely connected with the question of degeneration is that of the 

 size of animals, and its bearing on their structure and development ; a 

 problem noticed by many writers, but which has perhaps not yet 

 received the attention it merits. 



