EXPERIMENTAL MORPHOGENESIS 89 



origin : Eoux has shown that in the frog it is the accidental 

 path of the fertilising spermatozoon in the egg which, 

 together with the polar axis, normally determines the plane 

 of bilateral symmetry ; but this symmetry may be overcome 

 and replaced by another, if gravity is forced to act in an 

 abnormal manner upon the protoplasm ; the latter showing 

 parts of different specific gravity in the eggs of all Amphibia. 



The Neutrality of the Concept of " Potency " 



Now we may close our rather long chapter on the 

 distribution of potencies in the germ ; it has been made 

 long, because it will prove to be very important for further 

 analytical discussion ; and its importance, in great measure, 

 is due to its freedom from prepossessions. Indeed, the 

 concept of prospective potency does not prejudice anything ; 

 we have said, it is true, that limitations of potencies may 

 be due to the presence of specific parts of organisation in 

 some cases ; that, at least, they may be connected therewith ; 

 but we have not determined at all what a prospective 

 potency really is, what the term really is to signify. It 

 may seem that such a state of things gives an air of 

 emptiness to our discussions, that it leaves uncertain 

 what is the most important. But, I think, our way of 

 argument, which tries to reach the problems of greatest 

 importance by degrees, though it may be slow, could hardly 

 be called wrong and misleading. 



. THE "MEANS " OF MORPHOGENESIS 



We now proceed to an analysis of what may properly 

 be called the means of morphogenesis, the word " means " 



