ENCYSTATION OF ACTINOSPHARIUM BWICHHORNI. 413 
seems to obtain, irrespective of temperature, yet I incline to 
think that, in the cold culture, the chromatin content of the 
individual nuclei is greater than in the warmth. Mr. Smith, 
in his article already quoted, also finds that ‘in cysts built 
in the warmth the amount of chromatin is absolutely, as well 
as relatively, less than in the other cases.” He disregards, 
however, the comparative sizes of the nuclei in his cultures, 
considering that “such change of size” (of the nucleus) 
“could be brought about by an alteration in the conditions 
of tension in the cell, without any deeper changes in the 
physiological relations.” 
That the matter can be so lightly dismissed I do not believe, 
from what I have seen of the constancy in the relative 
nuclear-cytoplasmic proportions in my warm and cold cul- 
tures. An explanation is suggested by Professor Hertwig’s 
Kern-plasma Relation. I must here recapitulate somewhat. 
According to Professor Hertwig, an encysting Actino- 
spherium loses about 95 per cent. of its nuclei in the earliest 
stages of encystation. Probably only 5 per cent. of the 
original nuclei will survive till the end of the mother-cyst 
stage, and pass on to further development. The manner of 
this nuclear elimination is not yet clear. Hertwig considers 
it unlikely that the reduction is usually the result of fusion ; 
and he also holds it for improbable that, under normal con- 
ditions, nuclei are thrust out bodily. ‘To this latter point I 
shall return later. What one actually sees is a gradual 
shrinkage of the nucleus; its membrane hangs round it like 
a loose sac, and it dwindles from about 14 4 to 6 w or less. 
At the same time the central chromatin-rosette becomes less 
and less distinguishable, and the nucleus stains almost uni- 
formly. In this “dead” condition it may remain for some 
time, but, under normal conditions, it disappears entirely 
before the primary cysts are formed. | 
Professor Hertwig’s theory of ‘ Kern-plasma Relation ” 
gives a possible reason for this nuclear reduction. He sup- 
poses a sort of mutual antagonism to exist between nucleus 
and cytoplasm, such that, during high function in the cell, 
