236 Science Religion and Reality 



mechanism could be thought of which would satisfy this demand, 

 so, as Heidenhain had found for the kidney, it was necessary to 

 invoke a vital force. There is an obvious advantage in basing 

 these speculations upon experiments, for there is then something 

 definite to argue about, but there is also the disadvantage that the 

 facts may not be really what they appear, and improved technique 

 may leave the philosophical superstructure in mid-air without any 

 outward and visible means of support. Haldane, however, only 

 based his views partly upon experimental results. 



The fact which Driesch found incapable of explanation upon 

 mechanistic lines may be briefly stated as the power which a 

 developing embryo has of three-dimensional regeneration. If an 

 embryo which has developed as far as the blastula stage, in which 

 it is a hollow sphere of cells without any top or bottom, right or 

 left, is then divided into two or more parts with a sharp cut, each 

 half becomes later on one entire embryo. Thus, since there are 

 an infinite number of planes along which the cut might have gone, 

 any one part of the embryo must know what the other parts are 

 going to do, and, moreover, must be prepared to perform almost any 

 function. In other words, until a very late stage in development 

 each single cell must have the potentiality of turning into any other 

 cell, according to the necessity of the whole body. Any one cell 

 might become a liver-cell, a blood-corpuscle, or a constituent of 

 bone tissue according to the demands made upon it : demands, too; 

 incapable of being foreseen, for the plane of the experimentalist's 

 cut is a matter of chance. " A very strange sort of a machine 

 indeed," says Driesch, " which is the same in all its parts." " It 

 is not possible," Driesch says, " to conceive of a machine being 

 divided in any direction and still remaining a machine." 



Driesch, as the result of innumerable such experiments, was 

 therefore led to regard the organism as a whole as the only possible 

 biological unit — a conception which Haldane later arrived at 

 independently. There seems to be a kind of autonomy not only 

 in the developing embryo but in all organisms, so that the normal 

 typical form and structure and function come into being whatever 

 the interference, provided that the interference is not too great. 

 There is a certain trend on the part of the organism, and if an 

 obstacle is placed in its way, the organism, quite apart from the 

 attributes of conscious life, seems to try first one way and then 

 another of overcoming it, as if moved on irresistibly by what has 



