ENCYSTATION OF ACTINOSPHERIUM EICHHORNI. 411 
I examined the cysts while they were in clove oil, and took 
measurements of their length and breadth—these measure- 
ments I found to be very constant so long as the culture was 
normal. Hven to the eye there was at once a quite striking 
difference between cysts from the warm culture and those 
from the cold. Those from the warm were noticeably the 
larger, and of more oval form, with a thin coat of silica: 
those from the cold were smaller, and more rounded in out- 
line; they lay together more compactly, and showed a tendency 
to greater production of silica. My measurements brought 
out the size-difference strikingly, the average length in the 
warmth being 118°5 uw, and the breadth 87°5 4, while in the 
cold the average length was 83°5 pw, and the breadth 77°5 pu. 
I had not taken the pains to measure the Actinospheria 
used for these cultures, nor had I observed whether fusion 
took place between two or more during the starvation period 
previous to encystation. I therefore cannot say that, in the 
compared cultures, the groups of cysts arose from exactly 
equally-sized individuals. Still, in a general way, I had 
chosen Actinospheria of about the same size. ‘Therefore, it 
is at least interesting to note that the average number of 
primary cysts formed by one individual was in the cold cul- 
ture 5, as compared with 3 in the warm. Seven or eight 
cysts In a group was not uncommon in the cold, but in the 
warmth was rare. In the warmth sometimes only two cysts, 
and twice only one cyst of large dimensions were formed by 
one individual. Nowif, as has been stated, the number of 
cysts formed depends on the number of nuclei remaining over 
from the reduction in the mother cyst, then this larger number 
of cysts formed at alow temperature must mean that, in the 
cold, a larger number of nuclei escape destruction. The 
smaller size of these cysts is the necessary result of their 
greater number, there. being less cytoplasm available for each. 
Mr. Smith’s experiments gave the same general result. 
(‘ Biometrica,’ vol. 11, 1903). 
To obtain measurements of the nuclei in the primary cysts, 
I made sections, 10 thick, of the cysts that I had previously 
