Heredity and its Bearings on Atavism. 131 
who published an exhaustive account of his experimental 
researches on Infusoria—researches specially undertaken to 
throw light on the functions of the nucleus. This author has 
arrived at the following conclusions :—* The physiological 
significance of the nucleus is dependent only on its relations 
to metabolic changes occurring in other parts of the cell. It 
influences the functions of the cell only by the part it plays 
in the metabolism of the cell, and only hereby does it take 
an active part in the phenomena of cell-life.” “A nucleus 
cannot exist without its protoplasm, nor can the protoplasm 
exist without its nucleus—they are both mutually inter- 
dependent.” 
Verworn illustrates his view by the accompanying figure, 
which represents a cell with its nucleus. Each arrow indi- 
cates a set of nutri- 
tive materials in pro- 
cess of metabolism. 
The cell receives a 
number of materials 
‘from without, a por- 
tion of which (a) is 
acted upon by the cell 
protoplasm; analytic 
andsyntheticchanges 
are brought about 
which lead to a 
part of the absorbed Fig. 3. 
material being got Fig. 3.—Diagram of cellular metabolism. 
rid of as effete (After Max Verworn.) 
matter (>), while the remaining portion is partly made use 
of by the cell-plasm (¢), and partly conveyed to the 
nucleus (d). The nucleus is represented as further receiving 
certain substances from the exterior, which pass unchanged 
through the cell-plasm (¢). Those substances (d and e) 
which reach the nucleus, in their turn undergo metabolic 
changes—they are partly made use of by the nucleus 
itself (s), partly handed over to the cell-plasm (i), and partly 
removed as effete matter (7). 
The diagram fully illustrates the conceptions of Verworn, 
