126 f. AAONEL TAVEER [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 frequently 
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, ete. 
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, 
exeretes 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 
svould be as economical as the specialisation of food supply among 
