218 SYMBIOGENESIS 



correlative aspect, an alteration of arrangement among certain momenta 

 whereby these parts are impelled to their new positions. At the same 

 time that a force, acting differently on the different units of an aggre- 

 gate, changes their relations to each other; these units, reacting differ- 

 ently on the different parts of the force, work equivalent changes in 

 the relations of these to one another. Inseparably connected as they 

 are, these two orders of phenomena are liable to be confounded together. 

 It is very needful, however, to distinguish between them. 



We have seen that nutritional habits are particularly 

 responsible for changes of momenta and of correlations, and 

 that such changes are connected with a parallel set of changes 

 in domestic and biological symbiosis. 



Certain mammalia, for instance, having in the past for 

 reasons we need not here go into, made the change from cross- 

 feeding to in-feeding ; this in course of time implied new 

 physiological momenta as outwardly expressed in corres- 

 ponding changes of form and of structure. Thus there arose 

 great canine teeth with vast fangs, with concomitant corre- 

 lated changes upon the whole anatomy of the animal. 



As was pointed out in Evolution by Co-operation, the 

 coming of vast teeth and fangs entailed an excessive blood- 

 supply to these parts at the expense of that formerly (normally) 

 going to the brain, and in the long run in-feeding leads to that 

 huge increase of size through geological periods which is so 

 puzzling a phenomenon to modern Biology, seeing that it is 

 generally the reverse of useful even to the particular species. 

 Were it a normal process and congruous with the requirements 

 of progressive evolution generally, such an increase of size 

 should be "useful " and attended by a commensurate develop- 

 ment of brain, which manifestly, however, it is not. But the 

 supply of food-force in these instances is not adequate enough 

 for purposes of domestic or of biological symbiosis to produce 

 permanently desirable normal results. The " simultaneous 

 re-distribution undergone by the forces " is such as eventually 

 to produce stimulation of some organs at the expense of 

 others, i.e., an unwholesome asymmetry. Predaceous feeding 

 eventually produces absurdly overgrown bodies with absurdly 



