535 
cleata are as fine. The greater thickness of the body in O. macronucle- 
ata must make its nuclei a little more difficult to study. 
Observation of the nuclei of O. antilliensis has shown a very inter- 
esting condition as to the chromosomes, which my studies of O. intesti- 
nalis and O. caudata did not reveal. There are two distinct sets of 
chromosomes, one massive and the other granular, both sets lying just 
beneath the the nuclear membrane (cf. figs. 12 and 13). Leger and 
Duboscq have described similar granular linear chromosomes and 
massive “parachromosomes” in O. saturmalis. I can confirm their. de- 
scription of these conditions in O. saturnalis from my own study of this 
species. Comparisons between O. saturnalis and O. antilliensis must be 
left for the more complete paper now in preparation. 
The massive chromosomes in O. antilliensis resemble those of O. 
intestinalis and O. caudata. Some are large, some small, some interme- 
diate in size. As in O. intestinalis and O. caudata there are several 
characteristic sizes and shapes, and chromosomes of these sizes and sha- 
pes are seen in every nucleus during the anaphases of mitosis. During 
the anaphase stages the several diverse chromosomes at one end of the 
nucleus correspond each to a chromosome of the same size and form in 
the other end of the same nucleus, and the pattern thus shown in one 
nucleus is closely reproduced in any other nucleus in a corresponding 
stage of mitosis. The massive, and also the granular daughter chromo- 
somes, are connected in pairs across the equator of the nucleus by easily 
staining threads that aid in determining which two chromosomes belong 
to each pair. 
The granular chromosomes consist of lines of granules which are 
hardly larger, but stain more deeply, than the achromatic granules. The 
achromatic granules are found thru the whole nucleus, not being con- 
fined, as are the chromatin elements, to the superficial layer. The gra- 
nular chromosomes differ considerably in the number of granules they 
contain. One cannot have entire confidence in the accuracy of his count- 
ing of these granules, but it can be said that in some of the longer of 
these chromosomes there are more than twice as many granules as in 
the shortest. The chromosomes of any one pair, one at each end of the 
spindle, are alike. 
I have not yet reexamined the nuclei of Opalina intestinalis and 
O. caudata with sufficient care to be sure of the condition of the granu- 
lar chromosomes in these species, tho it is evident they are present. Fresh 
material of these species is not obtainable in America. 
Interesting as is this remarkable double series of chromosomes in 
Opalina antilliensis, its interest in enhanced when we realize how differ- 
ent are the conditions in the multinucleate Opalinas. The accompa- 
