THE GREAT DEEPS 107 
be the case. The deep-sea animals have been 
found on the whole to be very similar to others 
of the same families living on the shore or near 
the shore elsewhere, with, however, certain 
well-marked differences, which make them bet- 
ter fitted for life in their actual surroundings. 
Thanks to the efforts of the different ex- 
ploring expeditions and to the published rec- 
ords of their work, we have now some very 
definite ideas of the conditions of life at the 
bottom of the sea, and of the ways in which 
animals are adapted to them. 
Every expedition that has been sent out has 
carried more and more perfected apparatus 
for exploring the great depths. It has been 
found possible to bring up specimens of the 
lowest layer of the water, and of the actual sea- 
floor itself, as well as of the animals that lived 
there. Thermometers have been devised for 
registering the temperature, and instruments 
for measuring the pressure at different levels. 
THE DEEP DEEP SEA 
By the deep sea naturalists mean practically 
the floor of the deep parts of the sea and the 
layers of dark water near the floor. Compara- 
