272 M. M. Mercarr 
constriction. Stone (1900) and Borr (1907), on the other hand, are 
certain that they arise in the cytoplasm and that they do not in- 
crease by division. Srorc describes them as consisting of two parts, 
an outer envelope and an inner substance, the latter glycogen, the 
former a carbohydrate. Borr confirms Srouc, agreeing that the re- 
fractive bodies are probably reserve nutritive material. The mor- 
phological structure of the endosare spherules in Opalina, with their 
outer layer of granules and more lightly staining central-portion, 
resembles the structure of the refractive bodies of Pelomyxa and their 
interpretation as reserve nutrient material seems altogether probable, 
though they are not true glycogen. As already shown, the chro- 
matin spherules of Opalina and the macronuclear granules of other 
Ciliata may be comparable. If, then, the endoplasmic spherules of 
Opalina are derived from the chromatin spherules, our series of com- 
parisons would include the macronuclear granules of most Ciliata, 
the chromatin spherules in the nucleus of Opalina, the endoplasmic 
spherules of Opalina, and the refractive bodies in Flagellata and 
Foraminifera. There is a general resemblance also between the re- 
fractive spherules of Protozoa and the pyrinoids of plant cells. Both 
seem to be a reserve food supply and both are handed down from 
parent to child when the cells divide. We know nothing, however, 
to indicate any special connection between the pyrinoids and the 
substances in the nuclei of plant cells. 
Phylogeny of the nuclei of Ciliata. 
The question as to what in Opalina is the full homolog of the 
macronucleus in higher Ciliata can best be approached through a 
discussion of the evolution of the condition with two functionally 
diverse nuclei. The macronucleus of higher Czlata arises by the 
metamorphosis of a nucleus which has itself arisen by division from 
the micronucleus.) It is therefore phylogenetically a complete 
nucleus and not a mere mass of granules extruded from a nucleus 
and gathered into a group. The macronucleus seems to be speciali- 
zed in connection with the nutrition of the cell. It is able to di- 
vide, as does the micronucleus, in the vegetative divisions of the 
cell, but it takes no part in the special phenomena, interpreted as 
maturation, which preceede conjugation. The micronucleus, apparently 
1) NerEsHEimeR (1908) does not describe the origin of the macronucleus in 
Ichthyophthirius (species?). The remarkable phenomena which he does describe, 
if correctly described, make it improbable that the macronucleus in this species 
arises by metamorphosis from a micronucleus. 
