9O RALPH S. LILLIE. 



higher animals particular cell-structures like chromosomes may 

 become essential regulatory or determinative factors, controlling 

 the detailed character of the developmental proliferation, is in 

 no sense inconsistent with the general point of view here pre- 

 sented. All protoplasmic structures as they originate must 

 influence formative metabolism, as has been so ably pointed out 

 by Child ; and there is every evidence that the chromosomes have 

 a peculiarly intimate relation to the distribution of form-deter- 

 mining factors. Recognition of the part played by hormones in 

 development is also consistent with the present view. What 

 we are now attempting, however, is not to define the special 

 mechanisms governing the course of development in the higher 

 metazoa, but to indicate the nature of the more general physico- 

 chemical mechanism, common to all forms of living matter, 

 which forms the basis of its characteristic self-conserving and 

 proliferative properties. Any conception of the essential con- 

 stitution of living matter must first of all take its constant and 

 fundamental distinguishing peculiarities into account. Once 

 the living material has come into existence, with such properties 

 as these, it may serve as the basis for the development of diversity 

 and complexity of all kinds, as has in fact occurred in the course 

 of evolution. 



