LAP-DOGS' JAWS. 13 



bite would easily bring about a general enfeeble- 

 ment of the whole biting apparatus weakness 

 of the parts concerned favouring harmlessness. 

 Mr. Spencer maintains that the dwindling of the 

 parts concerned in clenching the jaw is certainly 

 not due to artificial selection because the modifica- 

 tions offer no appreciable external signs. Surely 

 hard biting is sufficiently appreciable by the 

 person bitten without any visual admeasurement 

 of the masseter muscles or the zygomatic arches. 

 Disuse during lifetime would also cause some 

 amount of degeneracy ; and I am not sure that 

 Mr. Spencer is right in entirely excluding economy 

 of nutrition from the problem. Breeders would 

 not over-feed these dogs ; and the puppies that 

 grew most rapidly would usually be favoured. 



