DIVISION OF COLLAR-CELLS OF CALCAREA HETEROCCELA. 133 
greater development than this in the case of collar-cells; 
a glance at figs. 6 and 10 will make it clear how far removed 
it is in appearance from the long continuous coiled thread so 
universally seen in more developed types of karyokinesis. 
Speaking generally, the blepharoplast divides just before the 
above changes take place iu the nucleus, but here again 
slight variations in the time-relations are very often to be 
observed. The blepharoplasts gradually move apart, but 
may sometimes be joined for a time by a strand ; this stage is 
of rare occurrence and is illustrated in fig. 8. More often the 
blepharoplast divides and the daughter-blepharoplasts move 
apart without the junction between them persisting. These 
two little granules are destined to play the part of centrosomes 
in the coming mitosis, but do not show the radiations passing 
out from them which are so characteristic of most centrosomes. 
As time goes on they come to lie on either side ot’ the nucleus, 
and a spindle-apparatus is formed between them. In fig. 11 
an interesting stage is shown where the spireme is not yet 
quite complete and the first signs of the spindle can be seen 
arising between the controsomes on either side of the nucleus. 
The mitosis proceeds and the equatorial plate is formed, but 
the chromosomes are not very distinct. At this stage there 
grows out from the centrosomes on either side the first 
rudiment of the new flagella (figs. 12-16 and 21), thus 
exactly repeating the state of affairs observed in Clathrina 
coriacea. The diaster-stage (figs. 17-19) follows in due 
course, and the two poles of the spindle each with its mass 
of chromatin curve upwards through approximately a right 
angle (figs. 20 and 21). 
The centrosome-blepliaroplast is still connected with the 
chromatin mass by a double strand (figs. 20, 21), which is 
the remains of the spindle. This connection persists as the 
double rhizoplast already noted and only disappears again 
just before the next division. In Clathrina this junction 
disappears and the blepharoplast is completely cut adrift 
from the nucleus during the vegetative life of the cell. The 
