PURITY OF THE GERM CELLS fe 
The minute study of the germ-cells, taken in connec- 
tion with modern experimental work on the methods 
by which inheritance takes place, shows a strong 
tendency to confirm Weismann’s view, so far as the case 
of distinct and definite characters is concerned. But 
if we regard such definite characters as having arisen 
by definite steps or mutations according to the view 
now gaining ground, the study of them will have no 
bearing upon the question of use-inheritance, since 
use does not lead to large and definite changes in the 
individual, but to comparatively small changes of a 
quantitative kind. 
There are some, including de Vries, who regard all 
fluctuating variations (individual differences) as being 
of the nature of acquired characters, and as being at 
the same time capable of hereditary transmission, 
although de Vries believes the amount of progress 
possible in this way to be strictly limited. Let us see 
if there is any way in which a transmission of such 
characters can be conceived of. 
It must be pointed out that the cells which make 
up an organism are not completely marked off and 
separated from one another ; on the contrary, it seems 
impossible to doubt that reactions may take place 
between them long after their first formation. Indeed, 
Sedgwick has shown that in a number of diverse kinds 
of animals there is never any sharply limiting barrier 
between cells at all, and this writer has gone so far as 
to speak of animals in general as being built up of a 
continuous network of protoplasm with nulcei at the 
nodes. In plants, too, though at first sight their con- 
