THE SPOUTING AND MOVEMENTS OF WHALES. (>48 



ing a wagon, and that even a man can sleep while marching. Tiiere is 

 nothing, therefore, which, a priori, could prevent our accepting this 

 hypothesis, but we have seen that the observations cited at the begin- 

 ning of this paragraph tend rather to cause us to hold that the 

 cetaceans do not sleep at all. If I dwell on this subject, it is merely 

 to show its interest and the small amount of data we possess for the 

 solution of the problem. 



C. MigrationH. — Cetaceans have often been seen in the open sea, 

 traveling straight ahead, without sounding; in these cases they are 

 following a course in search of a new feeding place, or perhaps for 

 the needs of reproduction. 



CONCLUSIONS RELATIVE TO MOVEMENTS. 



From this brief inquiry relative to the movements of cetaceans, it 

 results that these movements vary according to the species. It is this 

 point which seems to me especiall}^ important from a practical point 

 of view, and in the chapters which follow I shall demonstrate, with 

 suitable proofs, that it is certainly so, for the species I have been able 

 to study. I la}^ down the principle, therefore, that the movements of 

 cetaceans in the water are specific. In combining the results derived 

 from observation of movements, with data supplied b}" dimensions, 

 form, and color, one becomes able to recognize readily ever}' kind of 

 whale with as much certainty as if one had the animal at one's disposal 

 to dissect — an opportunity which presents itself but rarely. 



THE DEPTH TO WHICH CETACEANS DIVE. 



I will pass in closing this chapter to the consideration of a funda- 

 mental question in the biology of the Cetacea — the depth to which 

 they dive. There arc no direct observations for the solution of this 

 problem and those cetologists who mention it incidentall\^ content 

 themselves with assertions without proofs. All give very high fig- 

 ures, and Kiikenthal (1900, p. 197) pretends even that cetaceans can 

 dive more than 1,000 meters (3,281 feet), but without mentioning on' 

 what he bases this assertion. I do not believe that this depth can ever 

 be attained by these animals; on the contrary, I believe that the}' can 

 not exceed a maximum depth of 100 meters (328 feet). Let us examine 

 into what takes place when a cetacean dives. 



First. — The pressure of the water: It is necessary not to forget that 

 the cetaceans have an aerial respiration —that their pulmonary cavities 

 are filled with air. On tiie other hand, we know what takes place when 

 a mammal is submitted to a pressure of several atmospheres; the gases 

 dissolve in large quantities in the blood, and when the pressure is 

 relieved suddenly the surplus of dissolved gas can not be eliminated 

 by the lungs; the gaseous bubbles form in the capillaries, which 

 arrest the circulation of the blood and cause death. For man, the 



