460 On Archcesthctism. [June, 



" A complementary loss of growth force may be seen in the ab- 

 sence of superior incisor teeth and digits in ruminating Mammalia, 

 where excessive force is evidently expended in the development 

 of horns, and complication of stomach and digestive organs. The 

 excess devoted to the latter region may account for the lack of 

 teeth at its anterior orifice, the mouth ; otherwise, there appears 

 to be no reason why the ruminating animals should not have the 

 superior incisors as well developed as in the odd-toed (Perisso- 

 dactyl) Ungulates, many of which graze and browse. The loss 

 to the osseous system in the subtraction of digits may be made up 

 in the development of horns and horn-cores, the horn sheath being 

 perhaps the complement of the lost hoofs. It is not proposed to 

 assert that similar parts or organs are necessarily and in all groups 

 complementary to each other. The horse has the bones of the 

 feet still further reduced than the ox, and is nevertheless without 

 horns. The expenditure of the complementary growth force may 

 be sought elsewhere in this animal. The lateral digits of the 

 EquidcB are successively retarded in their growth, their reduction 

 being marked in Hippotherium, the last of the three-toed horses ; 

 it is accompanied by an almost coincident acceleration in the 

 growth nutrition of the middle toe, which thus appears to be com- 

 plementary to them." 



II. The Office of Consciousness. 



If the law of modification of structure by use and effort be 

 true, it is evident that consciousness or sensibility must play an 

 important part in evolution. This is because movements of ani- 

 mals are plainly in part controlled by their conscious states. The 

 question as to how many of the actions of animals are due to 

 conscious states at once arises. It is well known that most of the 

 more strictly vital functions are unconsciously performed. Not 

 only these, but many acts which have to be learned, come to be 

 performed in unconsciousness. Further, movements appropriate 

 to needs which arise at the moment, and which are ordinarily 

 termed voluntary, because they require the introduction of more 

 or less of the rational faculty, are readily performed by verte- 

 brated animals deprived of a brain, through the agency of the 

 spinal cord alone. 1 The history of the origin of these move- 

 ments must then be traced. 



The movements of living beings generally possess the peculi- 

 arity of design, in which they differ from the movements of non- 

 living bodies. That is, their actions have some definite reference 

 to their well being or pleasure, or their preservation from injury 



1 Such expressions as "unconscious sensibility" and " unconscious will are 

 used here, as being self- contradictory in terms and without meaning. 



