1885.] 
Strassburger' s Theory of Generation. 
6 75 
external plasma is concerned with adaptation. Molecular 
excitements are propagated from the nucleus-cell to the 
surrounding cytoplasm, which, on the one hand, control the 
processes of the transformation of matter in the cell, and, 
on the other, impart the peculiar character of the species to 
the growth of the cytoplasm conditioned by nutrition. The 
cytoplasm in return reacts upon the cell-nucleus, exciting 
its divisions and determining its nutrition. 
In opposition to Nussbaum and Weismann, and in accord 
with Naegeli, Strassburger assumes that the germinal sub- 
stance in the course of ontogeny does not pass unchanged 
into the organism (the substances determined for thegerminal 
cells being early separated from the remaining substances of 
the body), but that they are produced anew from the modified 
idioplasm by a process of reverted development. In a cer- 
tain sense the nuclear substance fulfils the conditions which 
Weismann demands from germinal substance, for it passes 
through the body in a separate condition, in so far that the 
dynamic influences proceeding from the cytoplasm and 
acting upon it have little influence upon the specific attri- 
butes of the nuclei. The individual acquired properties 
remain connected with the idio-cytoplasm, and are transferred 
only along with this, as in the improvement of plants. In 
common with Weismann, Pfluger, and Naegeli, Strassburger 
opposes the exaggerated importance attributed to individu- 
ally acquired properties, and, with Naegeli, he seeks for the 
causes of the changes of the organism not in outward, but 
in inward fadlors, namely, in the molecular forces inhering 
in the substance. 
In copulation only those elements of the generative cell- 
nuclei become mixed which are not morphologically differen- 
tiated. The nuclear threads on both sides do not coalesce, 
but merely apply themselves to each other. Not until the 
fission of the germinal nucleus does the process of coalescence 
ensue in the secondary nuclei. In the germinal nucleus 
preparing for division the framework contracts to a short 
thread, which is resolved into segments. These again are 
split up longitudinally, and these halves of each segment are 
distributed equally to the two secondary nuclei. 
In these the nuclear thread segments coalesce with their 
ends to a single nuclear thread, which is thus composed half 
of segments derived from the father and half of those 
springing from the mother. These pieces must have been 
again derived each from both grandparents. It is clear that 
both these parts become the smaller the more remote the 
generations to which they belonged. The portions of the 
