74 THE GERM-PLASM THEORY 



was no miniature model in the germ. According 

 to this school there arose in the simple substance of 

 the germ, from the formative powers inherent in 

 it, a long series of stages of development, each 

 one more complex than that which preceded it, 

 until the perfect form was arrived at. Weismann 

 and Hertwig may be looked upon as the exponents 

 of the modern forms of these two views. The 

 former believes that development is the becoming 

 visible of complexity previously hidden from us ; 

 the latter that it is a new formation of complexity. 



" I assume [says the former] that the germ- 

 plasm consists of a large number of different living 

 parts, each of which stands in a definite relation 

 to particular cells or kinds of cells in the organism 

 to be developed, that is, they are ' primary con- 

 stituents ' in the sense that their co-operation in 

 the production of a particular part of the organism 

 is indispensable, the part being determined both 

 as to its existence and its nature by the pre- 

 destined particles of the germ-plasm." Vol. i. 355. 



Hertwig, on the contrary, holds that 

 " the embryological development of an organism 

 is no mosaic work. The parts of an organism de- 

 velop in relation to each other, the development 

 of a part depending upon the development of the 

 whole."* 



It will be seen that these two views are diamet- 

 rically opposed to one another. 



Let us now follow Weismann's theory a little 



* The Biological Problem of To-Day. Translated by Chalmers 

 Mitchell. Heine mann, 1896. 



