Opalina mitotica. 87 
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 reformig into a new nucleus or new 
nuclei, or, as in Ohromidina (GONDER 1905), all the chromatin passing 
into the eytoplasm where after a time a 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 chro- 
matin and consequent hypertrophy of some parts during the 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 
reestablish 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 
remains minute and hardly shares in the activities of growth. The 
divergence must have occured in a binucleated (or multinucleated) 
condition. We have in Opalina such a binucleated (or multinucleated) 
form. Im what way could its condition with similar nuclei be 
changed into a condition with dissimilar nuclei? 
“First let us note again the fact that the nuclei of the binuclea- 
ted Opalinae are often slightly dissimilar in regard to mitosis, one 
being often in a slichtly more advanced condition than the other. 
There is a similar divergence in regard to the formation of the 
probably nutritive chromatin spherules, one nucleus showing these 
in a more advanced stage of formation. The exact balance of the 
two nuclei seems already somewhat disturbed in Opalina. 
“May we conceive this divergence as going further, the nutri- 
tive chromatin becoming hypertrophied in one nucleus and not in 
the other, the second nucleus ultimately giving up almost all its 
connection with nutrition and becoming much smaller, giving us 
ultimately the condition seen in higher Cikiata with very divergent 
micro- and macronuclei? 
“One thing seems to stand in the way of such an interpretation 
so far as Opalina is concerned: in the division of Opalina one whole 
