248 INITIATIVE IN EVOLUTION 



of the anatomist whose Arboreal Man has attracted so much 

 attention. Speaking of the arboreal habit in the phylogenetic 

 history of mammals he asks the question, " How did this factor 

 enable that particular stock to acquire supremacy ?" and says 

 that it will be answered as far as it is possible, by the study of the 

 influence of the arboreal habit upon the animal body ; which may 

 be put in another way as the production of reflex-arcs suited thereto 

 (p. 3.) Of the muscle groups of fore and hind limbs he says, "With 

 a simple arrangement of anatomical parts a slight shifting of muscu- 

 lar origins has turned a perfectly mobile second segment into a 

 supporting segment constructed upon very simple lines : that these 

 changes are those produced by the demands of support from the 

 hind -limbs in tree-climbing seems obvious " (p. 6) ; of the position 

 of uprightness upon a flexed thigh of an arboreal man, " It is tree- 

 climbing which makes this posture a possibility " (p. 63). " But 

 it is not to be doubted that the underlying principle is clear enough, 

 that the arboreal habit develops the specialised and opposable 

 thumb and big toe " (p. 71). " Even before the power of grasp 

 is developed, we may imagine the dawn stages of educational 

 advances initiated by hand -touch " (p. 159). " Tactile impressions 

 gained through the hand are therefore perpetually streaming into 

 the brain of an arboreal animal and new avenues of learning about 

 its surroundings are being opened up as additions to the old factory 

 and snout-tacile routes " (p. 160). He asks also the pertinent 

 question, and says at least a partial answer to it can be given, " Did 

 the cerebral advance create the physical adaptations, or did the 

 physical adaptations make possible a cerebral advance ? " (p. 196). 

 Two more statements from this chapter show what the answer 

 to this question from the anatomist would be — " and again in the 

 evolutionary story we are forced back to consider a combination 

 of seemingly trivial, and apparently chance associations : in this 

 case the dawning possibilities of neo-pallial developments combined 

 with the physical adaptations due directly to environmental influences" 

 (p. 198). I have ventured to underline this passage. 



I regret the necessary length of these quotations but, on account 

 of them, can the better be suffered to finish this study, when I 

 briefly consider certain well-known nervous reactions in the cat 

 and dog as to their probable origin. It would be a highly interesting 

 thing to hear an exposition by an expert of all the reflexes and reflex- 

 arcs of such a system as those which in a cat, dog, ape, or man are 

 concerned with the passage of a morsel of food from the mouth 

 through all its chequered and varied career till it undergoes meta- 

 bolism and excretion, but I could not do it if I would, and would 



