Opalina. 247 
and fibrous appearance exactly similar to that seen in the endosare 
spherules. I am somewhat puzzled by this observation. Under all 
other conditions the two sorts of spherules seem very distinct. To 
most stains they react in an utterly different way (cf. the table in 
the appendix). It is difficult to belive that the bodies in the ectosare, 
which with iron-haematoxylin show this structure, are really the 
ordinary ectosare spherules. They are not endosare spherules which 
have been misplaced by the microtome knife, and they cannot be 
endosare spherules which have wandered unmodified into the ectosare, 
for in sections stained with differential stains one never sees endosare 
spherules in the ectosarc. These conditions sometimes seen in sections 
stained with iron-haematoxylin are not enough to indicate that the 
ectosare spherules arise from the endosare spherules. They are far 
more probably formed in situ. 
Splitting of the chromosomes. 
PritzNner (1886) is the only student who has described splitting 
of the chromosomes in Opalima, and all more recent workers agree 
that he was mistaken in his description. The chromosomes do not 
form into a definite equatorial plate and then split, as he described 
for O. ranarum. I find no convincing evidence of splitting of the 
chromosomes at any stage of the mitosis, but in sections of O. entestinalis 
and O. caudata, stained with iron-haematoxylin, one often sees, in 
the early telophases, a condition that suggests that the chromosomes 
may possibly be splitting (Fig. 86, Pl. XX). The chromosomes, when 
seen in side view, have a lighter axis and darker edges. Close 
observation shows that the darker appearance of the edges is due 
to the presence there of deeply staining granules which are absent 
from the axis of the chromosome. It would seem very simple to 
find cross sections of chromosomes in this condition and to determine 
definitely if we do have here a true splitting involving a division of 
the granules, but. so far, I have failed to obtain convincing pictures. 
Licer & Dusoscg (19046) describe for O. satwrnalis the for- 
mation of an equatorial ring and its division which they interpret 
as equivalent to the ordinary splitting of the chromosomes (Text 
Fig. IV, B, C, D). To this we will return. 
Nuclear conditions in other species compared with those 
in O. intestinalis. 
The nuclear conditions in O. caudata are so similar to those in 
O. intestinalis that but one point needs mention, namely, that the 
