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 better 

 fitted for life in their actual surroundings. 



Thanks to the efforts of the different ex- 

 ploring expeditions and to the published records 

 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 register- 

 ing 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. Comparatively 



