Case of Mitotic Division in Amocha proteus Pall. 55 
pl. II.: its endoplasm is clear and limpid, containing large crystals which 
are for the most part bipyramidal; its nucleus, in the resting condition, 
is similar to that figured by Leidy' and also by Calkins”; and it feeds 
voraciously upon diatoms (Figs. 1 and 2). This is a point of physiological 
interest, as the other so-called types of this species do not so feed. 
MATERIAL. 
The material in which the specimen was found was obtained in December 
1912, from Mr T. Bolton of Birmingham, to whom I had described the 
various types, remarking upon the one required. He found this latter, 
living as a persistent culture of its kind, in a pond at Lapworth, and he 
has supplied me with this single type regularly for months. 
About the end of December I was on the look out for cysts, of which 
I had obtained a large number in the early part of that year (February 
1912), consequently each incoming supply was watched with more than 
usual care. On 2nd January 1913, the amoebe were covering them- 
selves with debris and diatoms—a phenomenon which precedes encyst- 
ment. This I had watched in single cases in the previous November, 
and since the amoebe emerged from these little nests, instead of really 
encysting, I termed this temporary retreat a “pseudocyst.” During this 
month of November, I had turned out several amoebe from these 
pseudocysts; but on one occasion, while being closely observed after such 
a proceeding, the amoeba was seen to divide, the whole process taking 
about fifteen minutes; but during this time the nucleus was not visible, 
owing to the density of the protoplasm in its contracted state, and to the 
presence of numerous food particles. A few minutes after the daughter- 
amoebe had snapped asunder, a nucleus, typically proteus-like, was seen 
in each. In no case of division—and several now have passed under 
my observation—have I yet seen the living nucleus in the state 
of mitotic division; however, Awerinzew® states that he has seen every 
important phase in such a division, in the lving organism. 
After such an experience, the presence of pseudocysts in January would 
have suggested division had I not been expecting the amoebe to encyst. 
A few buried amoebz were isolated in a watch-glass with water-culture, 
diatoms, and a small amount of debris—an inducement to encystment—and 
left in a quiet undisturbed condition for a few days, in a fairly constant 
! Fresh-water Rhizopods of North America, 1879. 
? Calkins, loc. cit., plate 3, fig. 13. 
3 Awerinzew, loc. cit. 
