EXPERIMENTAL MORPHOGENESIS 85 



It is true, some sorb of regulation occurred, but that is 

 included among the factors of ontogeny proper. 



We shall afterwards study more fully and from a more 

 general point of view this very important feature of 

 " primary regulation " in its contrast to " secondary regula- 

 tion " phenomena. At present it must be enough to say 

 that in speaking of the restriction of the implicit potencies 

 in form-building we refer only to potencies of the primary 

 type, which contain within themselves some properties of 

 a (primary) regulative character. 



The Morphogenetic Function of Maturation in the Light of 



Recent Discoveries 



Turning again to more concrete matters, we shall first 

 try, with the knowledge acquired of the potencies of the 

 blastoderm and the so-called germ layers of Echinus, to 

 understand certain rather complicated results which the 

 experimental morphogenetic study of other animal forms 

 has taught us. We know from our historical sketch that 

 there are some very important aberrations from the type, 

 to which the Echinus germ belongs, 1 i.e. the type with 

 an equal distribution of the potencies over all the blasto- 

 meres. We know not only that in cases where a regulation 

 of the intimate structure of the protoplasm fails to occur 

 a partial development of isolated cells will take place, but 

 that there may even be a typical disposition of typical cells 



1 The reader will remember (see page 65, note 1), that even the germ 

 of Echinus is not quite equipotential along its main axis, but it is equi- 

 potential in the strictest sense around this axis. The germs of certain 

 medusae seem to be equipotential in every respect, even in their cleavage 

 stages. 



