EXPERIMENTAL MORPHOGENESIS 55 



thinks, as in fact, all such theories, if fully worked out, 

 have carried their authors to vitalistic views. But vital- 

 ism is regarded by him as dethroned for ever. 



Under these circumstances we have a good right, it 

 seems to me, to speak of a dogmatic basis of Weismann's 

 theory of development. 



But to complete the outlines of the theory itself : 

 Weismann was well aware that there were some grave 

 difficulties attaching to his statements : all the facts of 

 so-called adventitious morphogenesis in plants, of regeneration 

 in animals, proved that the morphogenetic organisation could 

 not be fully disintegrated during ontogeny. But these 

 difficulties were not absolute : they could be overcome : 

 indeed, Weismann assumes, that in certain specific cases 

 and he regarded all cases of restoration of a destroyed 

 organisation as due to specific properties of the subjects, 

 originated by roundabout variations and natural selection 

 that in specific cases, specific arrangements of minute 

 parts were formed during the process of disintegration, and 

 were surrendered to specific cells during development, from 

 which regeneration or adventitious budding could originate 

 if required. " Plasma of reserve " was the name bestowed 

 on these hypothetic arrangements. 



Almost independently another German author, Wilhelm 

 Roux, 1 has advocated a theoretical view of morphogenesis 

 which very closely resembles the hypothesis of Weismann. 

 According to Eoux a minute ultimate structure is present 

 in the nucleus of the germ and directs development by being 

 divided into its parts during the series of nuclear divisions. 



But in spite of this similarity of the outset, we enter an 



1 Die Bedeutung der Kernteilungsfiguren, Leipzig, 1883. 



