392 SCIENCE PROGRESS 



seems reasonable at least to allow the possibility that all these 

 things have a common extra-physical source. Such a " vital 

 principle," if existent, would doubtless act in accordance with 

 ascertainable laws ; the task of biology would be to investigate 

 them, to trace exactly the limits between the physical and the 

 vital and to discover the effects of their interaction. So long- 

 as vitalism is not used to provide a facile explanation of any 

 phenomenon which is not otherwise readily explicable, some 

 such hypothesis may serve as a starting-point for further 

 inquiry and may give hope of providing a common basis for 

 phenomena as far apart as the segmentation of a sea-urchin's 

 egg and the mental and spiritual faculties of man. 



