THE LATEST STAGE 253 



lungsmechanik," as it is not very happily called. 

 Driesch found that if the essential part of the egg 

 of the sea-urchin (Echinus m^crot^tberculatus) were 

 separated into two cells, each cell divided and 

 developed in the normal way. For some stages, the 

 product of development resembled what would have 

 been obtained by cutting in half the product of a 

 complete egg, but soon the hemisphere became rounded 

 into a sphere, and a whole larva, smaller than usual, 

 but complete in all its parts, ultimately developed. 



Such phenomena as these, the facts of adaptation 

 to changes of environment, the restitution of injured 

 parts in adult organisms, acquired immunity, the 

 reproduction of complex beings by the hereditary 

 process, above all the marvellous properties of mind 

 and consciousness studied by psychology, cannot be 

 put on one side. They make it impossible for a grow- 

 ing number of biologists to regard life as a cumula- 

 tion of chemical and physical changes, and have gone 

 far to re-establish biology as an independent science. 

 They have led to the revival of the old hypothesis of 

 vitalism, or, as some now prefer to call it, of the 

 autonomy of life an old theory with a new name, 

 arising refreshed from its years of retirement with 

 stronger claims to notice. 



Still, the majority of biologists remain convinced 

 that physiology in its essence is but applied physics 

 and chemistry, and that, although we are yet far 

 from a complete account of the organism, it is ulti- 

 mately explicable with no reference to unknown prin- 

 ciples, such as vitalism, old or new. Whatever be the 

 truth, it is probable that this attitude will inspire 

 much of the work of the coming years. It must not 



