exxxviil Proceedings of the Asiatic Society of Bengal. [N.S., XV, 
quite apart from that which we have in the past made the 
basis of our zoological classifications. 
at is to say, a definite chemical personality, as definite 
in its way as that complex of morphological and psychological 
characters that goes to form our ordinary every-day concept of 
a mouse or an elephant. 
If the bodies of different animals are analysed, or if par- 
ticular organs or tissues are analysed, they are found to be by 
no means of the same composition in different genera ; and the 
same holds when the chemical behaviour of tissues is examined 
—such as the absorptive power of the blood for oxygen, or the 
action of the excretory organs. 
ammals, for instance, get rid of their nitrogenous waste- 
products in the form of urea, whereas in the Selachians there 
is a remarkable amount of this substance in the blood. Birds 
chitin, uric acid, or substances akin to guanine, to mention 
only three, and possibly in other ways that are not yet known, 
as very few cases have been examined. 
These chemical personalities of different species, though 
they may be indistinguishable to our unaided senses, are un- 
doubtedly distinguished by many parasites with the utmost 
clearness. There are innumerable cases where animal parasites, 
are good examples, and the same thing is seen in the vast 
number of insects that infest only one kind of plant or a few 
closely related plants. 
x 
chemistry whereby the degree of chemical relationship between 
organisms may be tested. 
fusca, but not with that of a tree-frog or a toad. Similar 
reactions hold with invertebrates, and my present purpose is 
merely to recall to you the fact that there exists here a whole 
. . 
personality underlying the morphological, and that the chemi- 
_ cal personality is of the two infinitel i 
