126 / LIONEL TAYLER [august 



There will thus be very little tendency for incoordinated variations to 

 appear, and this tendency will diminish with evolution of type. 



8. That organisms not uncommonly exhibit a more perfect organisa- 

 tion than their environment demands. — This statement is frecmently 

 associated with other similar objections, some of which, such as 

 definite variability, and varying degrees of capacity to vary in different 

 animals, have already been met ; it is also asserted that animals some- 

 times manifest at the earlier periods of their lives a higher condition 

 than at a later period, and that this higher earlier condition cannot 

 be explained by any assumption of reversion in the later stages of 

 growth, thus it is asserted that the infant ape is much nearer to man 

 than the adult ape, etc. 



All these assumptions have as a basis the conscious or half 

 conscious belief in some unknown internal force which is capable of 

 producing evolution of type independently of environment. To 

 Lamarckian and selectionist theories alike any such force, were it 

 proved to exist, would be largely fatal. 



It has been shown that an increasingly definite tendency in 

 organisms evolved through the principle of natural selection is what 

 on theoretical grounds one would be led to expect — that the preserva- 

 tion of a definite relation of one part to another becomes of increasing 

 importance with increasing specialisation. That this is actually the 

 case, the facts associated with " internal secretion " in man and the 

 higher mammals clearly prove. The thyroid, kidney, liver, pancreas, 

 testes, and ovaries, etc., have been shown to exert some remarkably 

 important influence on the nutrition of the whole body, and this influ- 

 ence in the case of the thyroid, and less certainly in other organs, 

 has been found to be produced through the throwing off of certain 

 products into the circulation which are necessary to the metabolism of 

 the whole body. 



On any theory of complementary specialisation of parts such facts 

 are easily understandable. A chemical circle of nutrition would be the 

 most economical way of maintaining tissue activity ; if each organism 

 can act chiefly on some particular substance, one organ or tissue re- 

 quiring a more complex food material than another to carry on its 

 metabolism, then the waste product of one organ might be used as 

 a food product by the next in this food series, until the last organ 

 of this series, having obtained all the energy from this material, 

 excretes this simpler substance, which cannot be further utilised by 

 the body, into some channel where it is got rid of. Some such 

 hypothesis is necessary to explain the facts, and the increasing series of 

 progressively simpler products, although still incomplete, that have 

 been obtained, which are allied to uric acid and other substances, lends 

 considerable support to this theory. There would be thus a serial 

 specialisation of food supply among the tissues of each organism which 

 would be as economical as the specialisation of food supply among 



