THE STRUCTURE OF PROTOPLASM 
299 
mosome size and number, though it is safe enough to assume that his 
binucleated cells of Spirogyra contain twice the number of chromosomes 
found in the uninucleated cells. 
Conklin finds that the actual size of the chromosomes in the macromeres 
and micromeres of Crepidula varies with the size of the nucleus in which 
they lie but in lesser degree. ''The average volume of the chromosomes 
from the larger nuclei is 5.2 cubic ju and of those from the small nuclei about 
2.6 cubic yi. While the volumes of the nuclei as a whole are to each other 
as about 5 :i, the volumes of their individual chromosomes are to each other 
as 2:1. There is a tendency to constancy in chromosome size, and yet, 
"just as the size of the nucleus is connected with the volume of the cyto- 
plasm in which it lies, so the size of the chromosomes is connected with the 
volume of the nucleus from which they come." There is a tendency to a 
constant chromosome-nucleus relation of mass just as there is a nucleo- 
cytoplasmic relation of mass. 
If in embryological and later development there were a gradual reduction 
in the size of the nuclei, a corresponding reduction in the size of the chro- 
mosomes might be taken as evidence of a distribution of tissue determiners 
in the crude Weismannian sense, but while, as Conklin shows, there is no 
nuclear growth of 100 percent after each division there is a growth of five 
to nine per cent in the volume of the nucleus with each division during early 
cleavage and a growth of one percent during later cleavage. 
Of course these early divisions studied by Conklin and others relate to 
the development of the general symmetry relations and the Anlagen of 
systems and organs of the mature organism rather than to the production of 
the definitive Anlagen for the tissues. For plants at least the totipotence 
of the cells of the adult is evidence against the use of mass relations in 
the germ plasm at different stages of ontogeny as proof of its corpuscular 
constitution. 
Meek's rather crude conception of a definite width increase in the chro- 
mosomes as we pass from the lower to more highly specialized organisms 
has apparently been refuted by Farmer's more careful measurements and 
analysis. Farmer finds that in Primula Kewensis the size of the nucleus 
varies with the number of chromosomes which go to make it up rather than 
with the total mass of the chromatic material. As quoted in the table 
above, the form of Primula Kewensis with double the chromosome number 
of its parents has larger nuclei but the total mass of its chromatin is the 
same. The doubling of the chromosome number has been brought about 
by dividing each chromosome of the parent species into two equal chromo- 
somes. The size of the nucleus is in some degree influenced by the number 
of chromosomes rather than by the mass of chromatin as such. As Boveri 
holds, the surface area of the chromosomes rather than their total mass 
appears to be significant in influencing the nucleo-cytoplasmic mass relation. 
The measurements of the mass of the germ plasm at various stages of 
