548 JOURNAL, BOMBAY NATURAL HISTORY SOCIETY, Vol. VIII. 
completely cut off by the overlying water. Even in the Bay of Bengal, ata 
depth of 20 to 30 fathoms, there isa fall of temperature, compared with 
the temperature at the surface, of 2° to 3°. At 200 fathoms in the Bay of 
Bengal the thermometer would stand all the year round at about 55° Fahr., 
at 2,000 fathoms it stands all the year round at about 35° Fahr. 
To get an idea, then, of what the ocean-bed is like, we must imagine great 
plains, thousands of miles in extent, broken here and there by great valleys 
with very gently sloping sides, and by great mountain chains rising here and 
there into land. Minor inequalities of surface there are none, for the good 
reason that none of those forces which wear and sculpture the surface of con- 
tinents are in action. All is absolutely still, the darkness must be something 
that we can hardly conceive, and the temperature is near the freezing point. 
Plant life is of course absent, for plants can grow only in the presence of 
sunlight, so that we must imagine these vast dark silent plains and valleys to 
be absolutely bare. It is difficult to conceive that life can be found in the 
midst of such desolation ; and yet the researches of the last 20 years have 
proved that these cold, dark abysses teem with animal life, and are quite as 
well inhabited as the warm tropical reefs. Another factor has to be consi- 
dered. At the surface of the sea we are accustomed to the presence of the 
Superincumbent atmosphere only, a pressure which amounts to 14:7 Ibs. on 
every square inch of the surface of our bodies ; but water is infinitely heavier 
than air, and the animals which live at the bottom of the sea are subjected to 
the enormous pressure of the superincumbent ocean. Now,acolumn of water 
33'7 feet high exercises the same pressure as the whole column of the atmos- 
phere. Let us say in round numbers that a column of water 54 fathoms high 
exercises the pressure of one atmosphere ; then a column of water 2,000 
fathoms deep exercises a pressure of 363 atmospheres—a pressure that is of 
363 times 14:7 Ibs, or in round numbers of 2 tons 8 cwt. That is to Say an 
animal placed at a depth of 2,000 fathoms has to support a pressure of 2 tons 
8 cwt. on every square inch of the surface of its body. We now know the 
conditions under which animals live at the bottom of the ocean: (1) they are 
subjected to an enormous pressure : (2) they are absolutely deprived of sun- 
light ; (3) they live in a medium, the temperature of which is only slightly 
above the freezing point; (4) as there are no plants for them to eat they are 
carnivorous, and therefore highly rapacious. 
At the outset of this lecture we realized the fact that the forms of animals 
are profoundly modified by the direct action of the conditions of their in- 
organic environment ; and by means of these specimens I propose to illustrate 
some of the ways in which deep sea animals are modified by the peculiar cir- 
cumstances of their inorganic environment. Here I hand you a specimen of 
a deep sea fish, Tauredophidium heatii, Tauredophidium is closely allied to the 
blind fish that inhabits the underground waters of the great Mammoth Cave of 
Kentucky. You observe that it is quite blind. Underneath the skin, in the posi- 
