1 14 Journal of the Mitchell Society [December 



organizes. It organizes however in such a way as to prockice not a 

 half but the whole, that is, both right and left halves of the trunk of 

 the body. Thus the end result, the production of a typical form, may 

 be reached by very different paths. This variety in the fundamental 

 formative processes of which an embryo is capable makes it impossible 

 to think of development as at bottom a deterministic process, viz., as 

 one in which the embryo is a machine composed of (self-propagative) 

 parts each the material cause and origin of a particular portion of the 

 body. 



