" ARBOREAL MAN " 225 



certain that from reptiles similar to the Dinosaur Iguanodon, 

 the teeth of which have been found in some particulars to be like 

 those of the little living lizard from South America, called the 

 Iguan, the Birds have been derived . * But this Dinosaur was at any 

 rate herbivorous, and Sir Edwin's conclusion, if correct, in reality 

 points to a cross-feeding ancestry of the Birds.) However this may 

 be, it is certain that the " food-grasping power of the Primate 

 hand," which rendered unnecessary " the development of grasping 

 lips and a long series of grasping teeth," depended for its evolu- 

 tion upon temperate cross-feeding habits. Once the Primate 

 had, in virtue of " right " feeding habits, obtained a good start, 

 the symbiotic momentum easily carried him further along the 

 path of progressive development. Prof. Wood Jones says too 

 little about the nature of the food and overlooks the importance 

 of the " biological " method of getting it. He confines himself 

 to the mechanical side of the matter, and continues thus : 



When the mouth is the food-obtaining organ, there is a necessity for 

 its situation being advanced from the face, and especially that part of the 

 face in which the eyes are situated. A long snout with a mouth opening 

 far in advance of the eyes is a necessity in any animal which used its 

 mouth alone, in all the processes of obtaining food. The grazing herbivores 

 must carry their food-getting mouth far in advance of their eyes. The 

 long face of the horse may serve as a familiar example. The animals 

 which catch insects must have a similar structure, and the " snouty " 

 insectivorous Shrews are typical of such animals. The more the fore- 

 limbs serve to obtain or to hold the food, the less is this snout developed, 

 and I am terming the change which hand-feeding produces the recession 

 of the snout region. In herbivorous animals the transition is very easily 

 seen ; the long faced horse may be contrasted (solely from the point of view 

 of this function) with the short-faced squirrel which holds food between 

 its fore-paws. In carnivorous animals and mixed feeders another factor 

 comes in, for the mouth may be used, not only for grasping, but for killing 

 the food, or the fore-limb may take over this function in part. 



The grazing herbivores and the insectivorous Shrews 

 although some of the latter, such as the Tupaiadce, are arboreal 

 are, therefore, not in the line of progressive evolution. I have 

 already insisted on the inferiority of such types on the ground 

 of their relative backwardness in Symbiosis, and, as regards more 

 specially the latter, because of their in-feeding habits. The anti- 

 climax in snout development as between the puny fruitarian 

 and seed-distributing squirrel and the large-sized but plant- 

 carnivorous horse, is striking enough in illustration of the 



*Extincl Animals, pp. 200-203. 



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