Correlative Differentiation and Growth 47 
nection between the nuclei of the two partial networks 
belonging to these parts, a fact which renders these net- 
works in certain respects quite independent of one another 
if at the same time they do not come from a common 
principal branch. 
It would be ‘fa very important matter,” writes Delage 
“to know if secondary protoplasmic connections are 
formed between neighboring cells which are not sisters 
but which have been brought only secondarily into contact 
with one another, for example after an invagination in 
animals or through grafting in plants.” ?4 In the cases 
in which this did not occur one could then have the 
simultaneous and to a certain extent independent exist- 
ence of partial circulatory systems even though they lie 
close together or perhaps even enclose each other. 
Roux designates by the term “correlative or dependent 
differentiation” the complete or partial determination of 
development by reciprocal influences of epigenetic nature 
which become established, in a certain measure at least 
as he admits himself, between the cells. We can then 
designate these partial networks of the general cir- 
culatory system by the name “networks of correlation.” 
And we shall see that, conformably with our theoretical 
conjectures very many processes seem actually to prove 
that each of these networks is capable of existence by 
itself, independent within certain limits of other partial 
networks. 
Among the phenomena of correlative differentiation 
in development belong also those which are called com- 
pensatory growths. The investigations of Ribbert (1889) 
and his pupils upon the mammals have shown especially 
“Delage: L’hérédité et les grands problémes de la biologie gén- 
érale. P. 33. 
