SOME ASPECTS OF THE ADAPTATION OF LIVING 

 ORGANISMS TO THEIR ENVIRONMENT ^ 



By H. S. Halcbo Wabdlaw 



Our interests as members of this society lead us to consider the 

 relation of living things to their environment from many points of 

 view. We are on the whole, perhaps, more usually concerned with 

 the morphological aspects of this relation, but in this portion of my 

 address I wish to direct attention to certain chemical relationships 

 which subsist between the living organism and its surroundings. 

 After all, the chemical constitution of bodies may be regarded merely 

 as a more intimate expression of their morphology, as an expression 

 involving smaller units than those which are commonly studied by 

 visual examination. And in considering the material relationships 

 between a living organism and its environment we can not ignore 

 the relationships involving exchanges of energy. The conditions of 

 the former are to some extent determined by the requirements of 

 the latter. A survey of this kind would involve the discussion of a 

 wide range of questions. I wish to refer only to one or two of these 

 upon which biochemical information appears to have thrown light, 

 and to discuss one or two examples where adaptations have more 

 obviously been brought about by chemical adjustments. 



The thesis which I wish to submit to you may be expressed in two 

 statements: That the changes which living organisms have under- 

 gone in adapting themselves to their environment have had as their 

 object the maintenance unchanged of certain essential characters, and 

 that the organism which has most successfully adapted itself to its 

 surroundings is that which has acquired, to the greatest extent, the 

 power of adapting its environment to its needs. 



The most bewildering diversity of forms is met with among living 

 things. All these variations of structure may, no doubt, be regarded 

 as adaptations of one kind or another to the various environments in 

 which the different organisms are to be found. It will be as well, 

 therefore, to make clear at the outset what I wish to be understood by 



1 Reprinted by permission from the Proceedings of tlie Linnean Society of New South 

 Wales, vol. 55, pt. 1, No. 227, Apr. 15, 1930. 



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