508 
Proceedings of the Royal Society 
Fishes, and fish-eggs ; larvae of Echinoderms, and of many of the 
above creatures, &c. 
Most of these organisms live from the surface down to about 
100 fathoms.* In calm weather they swarm near the surface, but 
when it is rough they are to be found several fathoms beneath 
the waves. They are borne along in the great oceanic currents 
which are created by the winds ; and meeting with coral reefs, they 
supply the corals on the outer edge of the reefs with abundant food. 
The reason why the windward side of a reef grows more vigorously 
appears to be this abundant supply of food, and not the more 
abundant supply of oxygen as is generally stated. The “ Chal- 
lenger ” researches showed that oxygen was particularly abundant 
in all depths inhabited by reef-forming corals. 
When these surface animals die, either by coming in contact 
with colder water or from other causes, their shells and skeletons 
fall to the bottom, and carry down with them some organic matter 
which gives a supply of food to deep-sea animals. The majority of 
deep-sea animals live by eating the mud at the bottom. 
An attempt was made to estimate the quantity of carbonate of 
lime, in the form of calcareous Algae, Foraminifera, Pteropods, 
Heteropods, Pelagic Gastropods, in the surface waters. A tow-net, 
having a mouth 12J inches in diameter, was dragged for as nearly 
as possible half a mile through the water. The shells collected 
were boiled in caustic potash, washed, and then weighed. The 
mean of four experiments gave 2-545 grammes. If these animals 
were as abundant in all the depth down to 100 fathoms as they 
were in the track followed by the tow-net, this would give over 16 
tons of carbonate of lime in this form in a mass of the ocean one 
mile square by 100 fathoms, f 
* The Challengeridse, and many of the other members of Haeckel’s new order 
Phceodaria, certainly live deeper, as we never got them in the tropics except 
when the net was sent down to a depth of 200 or 300 fathoms. 
t Among the varieties of Foraminifera recognised by Mr Brady in the 
“ Challenger” collections, the following have a Pelagic habitat : — 
Pulvinulina Menardii. 
,, canariensis. 
, , crassa. 
,, Micheliniana. 
, , tumida. 
Pullenia obliquiloculata. 
Sphcerodina dehiscens. 
Caudeina nitida. 
Hastigerina Murrayi. 
,, pelagica. 
