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- 



