184 THE CONTINUITY OF THE GERM-PLASM AS THE 



I am of the opinion that the idioplasm cannot be re-transformed, 

 and I have defended this opinion for some years past T , although I 

 have hitherto laid especial stress on the positive aspect of the 

 question, viz. on the continuity of the germ-plasm. I have 

 attempted to prove that the germ-cells of an organism derive their 

 essential nature from the fact that the germ-plasm of each genera- 

 tion is carried over into that which succeeds it ; and I have tried to 

 show that during the development of an egg into an animal, a part of 

 the germ-substance although only a minute part passes over un- 

 changed into the organism which is undergoing development, and 

 that this part represents the basis from which future germ-cells 

 arise. In this way it is to a certain extent possible to conceive 

 how it is that the complex molecular structure of the germ-plasm 

 can be retained unchanged, even in its most minute details, through 

 a long series of generations. 



But how would this be possible if the germ-plasm were formed 

 anew in each individual by the transformation of somatic idio- 

 plasm ? And yet if we reject the ' continuity of the germ-plasm ' 

 we are compelled to adopt this latter hypothesis concerning its 

 origin. It is the hypothesis adopted by Strasburp-er, and we have 

 therefore to consider how the subject presents itself from his point 

 of view. 



I entirely agree with Strasburger when he says, ' The specific 



qualities of organisms are based upon nuclei ' ; and I further agree 



with him in many of his ideas as to the relation between the 



.nucleus and cell-body : ' Molecular stimuli proceed from the nucleus 



into the surrounding cytoplasm ; stimuli which, on the one hand, 



control the phenomena of assimilation in the cell, and, on the 



other hand, give to the growth of the cytoplasm, which depends 



upon nutrition, a certain character peculiar to the species.' ' The 



nutritive cytoplasm assimilates, while the nucleus controls the 



assimilation, and hence the substances assimilated possess a certain 



constitution and nourish in a certain manner the cyto-idioplasm 



and the nuclear idioplasm. In this way the cytoplasm takes part 



in the phenomena of construction, upon which the specific form of 



the organism depends. This constructive activity of the cyto-idio- 



plasm depends upon the regulative influence of the nuclei.' The 



1 This opinion was first expressed in my lecture, ' Ueber die Daucr <le* Lel>ens,' 

 Jena, 1882, translated as the first essay in the present volume. 



