192 EXPERIMENTAL EVOLUTION LECT. 



By means of instruments which he devised, he has 

 been able to compel animals to live under enormous 

 pressures, 500, 600, 800, and even 1000 atmospheres, 

 which corresponds to a depth of over 30,000 feet in 

 t?he sea, and he has seen that most animals, although 

 they withstand 200 or 300 atmospheres without 

 giving any signs of alteration in their vital functions, 

 pass into a state of latent life when the pressure 

 becomes higher. For instance, Vorticellae, under a 

 pressure of 600 atmospheres, become motionless ; the 

 cilia stop entirely, and the animal does not move at 

 all : the same phenomenon is observed even at lower 

 pressures (300), while other animals require higher 

 ones. The same phenomenon appears with different 

 species at different pressures. While some are killed 

 if they remain some time in this condition, others 

 revive when the pressure is diminished and becomes 

 normal ; they revive in more or less time. Actinia 

 plumosa may live a whole hour under 1000 

 atmospheres pressure : the animal seems to be dead, 

 and when taken out of the apparatus strikes the 

 spectator as being larger than before ; when weighed 

 it is seen to be twice as heavy as before the experi- 

 ment, water having doubtless been forced into its 

 tissues. But after some hours the animal is itself 

 again, has regained its normal weight and dimensions, 

 and is quite well. The same obtains with star-fishes, 



