46 THE DEPTHS OF THE SEA. [CHAP. I 
upon which animals can feed. This process is, how- 
ever, so far as we are at present aware, constantly 
effected under the influence of light. There seems 
to be little or no light at the bottom of the sea, 
and there are certainly no plants except such as 
may sink from the surface, but the bottom of the 
sea is a mass of animal life. At first sight it 
certainly seems difficult to account for the main- 
tenance of this vast animal population living with- 
out any visible means of support. Two explanations 
have been suggested. It is conceivable that certain 
animal forms may have the power of decomposing 
water, carbon dioxide, and ammonia, and re-com- 
bining their elements into organic compounds without 
the agency of light. Dr. Wallich supports this view, 
and in doing so he states that ‘“‘ No exceptional law 
is invoked, but, on the contrary, that the proof of 
these organisms being endowed with the power to 
convert inorganic elements for their own nutrition 
rests on the undisputed power which they possess 
of separating carbonate of lime or silica from waters 
holding these substances in solution.” * This, how- 
ever, seems scarcely satisfactory. All the substances 
employed in the nutrition of animals are offered to 
them finally in solution in water, and the abstrac- 
tion of these from their watery solutions cannot be 
regarded as a ‘ chemical separation.’ The broad dis- 
tinction still remains, that when carbon dioxide in 
solution is presented to a green plant in the sun- 
shine it can decompose it, while an animal cannot. 
I believe we have a simpler explanation. All 
sea-water contains a certain quantity of organic 
' North Atlantic Sea-bed, p. 131. 
