Vol. VIII, No. 2.]| The Freshwater Fauna of India. 45 
[N.8.] 
Il, 
now come to the second part of the lecture. Perhaps 
the simplest form that relations between different animals can 
take is the connection between hunters and prey. This con- 
nection is also by far the commonest that is found throughout 
the animal kingdom. In tropical fresh waters the struggle 
that goes on between the two great classes is a very keen one, 
for we find that whereas the number of individuals that live 
in a given area of water is probably less in warm countries 
than in temperate ones, the number of species among which 
the individuals are distributed is very much greater. This 
means to say, to a very large extent, that the methods by 
which prey is captured are much more highly specialized, and 
we must remember that an animal which is the natural prey 
of another is in very many cases itself the hunter of a third, 
so that the relations between the different species are, even 
in the matter of hunting, much more complex than they 
appear at first sight to be. This fact has a very practical 
application in tropical countries, for it indicates that if we 
wish to destroy the aquatic larvae of insects such as mosqul- 
as transmitters of disease, we must study not only all the 
stages of these insects but also all those of their enemies, and 
all those of the animals which prey on their enemies, and all 
those of the enemies of their enemies’ prey, and so on almost 
ad infinitum. Some day the Government of India may be 
forced to realize that the real problems which a civilized 
government must tackle are not political problems but sanitary 
ones. The capital of India has been changed, but the life- 
sanitary problems are fundamentally biological and chemical, 
not medical at all, and that the training of first-class biologists 
and chemists is just as important, just as difficult, lengthy and 
expensive a process as the training of first-class physicians and 
surgeons. : 
All of this is an introduction to the statement that we 
biologists are well aware that we have in India a large number 
of indigenous fishes that prey on mosquito-larvae. We 
by Captain Seymour Sewell, I.M.S., and ogeaigee 
giving descriptions and figures of those species of Indian 
that ha prove be particularly useful in this 
tion, or even the distribution, of fish of the kind is of very 
little u ir bi is studied in all its aspects. 
se unless their biology is studie sca ice es 
