Opalina. 2td 
holds in abeyance the functions connected with the nutrition of the 
cell, but the potentiality of these functions must be present, since 
daughter nuclei from the micronuclei are able to transform into 
macronuclei. Probably each type of nucleus is a complete nucleus, 
the nucleus especially connected with conjugation being slightly 
specialized by diminution of some of its functions and probably of 
the chromatic material upon which these functions rest. The macro- 
nucleus is specialized by the great development of its nutritive activi- 
ties and a corresponding great increase in the amount of chromatin 
especially associated with these functions. The specialization and 
hypertrophy of the macronucleus seems to have gone so far that it 
is difficult to secure conjugation of the macronuclei, and so, partly 
as a consequence, the macronuclei degenerate. The germinal (un- 
specialized) chromatin is so overbalanced by the nutritive (speciali- 
zed) chromatin in the macronuclei that it is unable to assert itself 
and bring about conjugation of these nuclei, and, without occasional 
readjustment such as is secured through conjugation, ultimate de- 
generation seems unavoidable. 
Before copulation or conjugation there seems to be quite gene- 
rally, among the Protozoa at least, a process of reestablishing the 
proper balance of the nutritive and other chromatin in the nucleus. 
It is apparently the nutritive chromatin which especially increases 
in amount during growth and ordinary vegetative divisions and the 
excess of this nutritive chromatin is gotten rid of before conjugation 
by the formation of chromidia, either the excess of vegetative chro- 
matin leaving the nucleus, or the excess of this specialized chro- 
matin being left in the nucleus, the ordinary chromatin going out 
into the cytoplasm and there reforming into a new nucleus or new 
nuclei, or, as in Chromidina (GonpeR 1905), all the chromatin passing 
into the cytoplasm where after a time part degenerates and the rest 
forms the generative nuclei. We doubtless do not know the full 
significance of these phenomena, but this. much seems probable, that 
there is division of labor between different parts of the chromatin 
and consequent hypertrophy of some parts during their periods of 
special activity. The specialization and hypertrophy of chromatin in 
connection with nutrition has gone so far in the macronucleus of 
Ciliata that it is simpler to secure a new macronucleus than to re- 
establish in the old macronucleus such a balance of the respective 
parts as will allow it to share in conjugation. 
What was the phylogenetic origin of the condition with two 
nuclei, one of which is highly developed for nutrition while the other 
