THE INTESTINAL PROTOZOA OF FROGS AND TOADS. 249 
becomes modified (fig. 59). It imcreases in size, reaching a 
diameter of 8-9 u, and nearly all the chromatin passes to the 
periphery, so that the inside is quite pale in a_ stained 
preparation, . 
I have usually met with these large forms in cultures of the 
feeces. I believe they are to be regarded as abnormal animals, 
overgrown from over-feeding, Such hypertrophied organisms 
seem to be incapable of either dividing or encysting. They 
have always died when kept under observation, 
In addition to the ordinary adult animal and the hyper- 
trophied form, there are also to be found amcebe of much 
smaller size (fig, 54). They are very much less common, but 
from the occurrence of all stages intermediate between them 
and the adults, I have no doubt that they are really the young 
forms. In addition to their small size they are characterised 
by possessing a different type of nucleus: for it is spherical, 
with a small but very distinct karyosomic granule (fig, 54), 
The diameter of the nucleus is 3-4 mu. 
Although the animals must sometimes divide very rapidly — 
judging from their great abundance occasionally—it is extra- 
ordinarily difficult to find stages in division in preparations. 
I have never seen division in the living animal, though it is 
not for want of seeking for it. In preparations also I have 
encountered but few dividing animals, and these, unfortu- 
nately were all in approximately the same condition, Fig, 55 
shows an organism with a very distinct dividing nucleus. 
From the occurrence of a binucleate stage (fig. 56), it is 
probable that fission of the cytoplasm does not take place till 
some time after that of the nucleus. It seems that the nuclear 
division is a kind of very primitive mitosis, similar to that 
seen in the cysts (see infra), where I have been able to follow 
it in considerable detail. 
Occasionally one encounters forms like that depicted in 
fig. 57, in which an amitotic division of the nucleus is very 
strongly suggested. But observation of the living animal 
shows that such a state has absolutely nothing to do with 
division, The shape of the nucleus is constantly changing 
