Vol. 8, 1922 
ZOOLOGY: M. BUNTING 
297 
2. Amoeba: — (fig. 1, B) a. Vegetative stage. Up to the present date 
the animal has always been observed to leave the cyst stage as an amoeba, 
never as a Tetramitus. The amoeba varies from 14^t to 48^6 in 
length. 
The rounded vesicular nucleus is usually 5 ^ to G m in diameter, and con- 
tains a caryosome 1/x to 2)U less in diameter; the pericaryosomal zone is 
usually clear but may contain a few granules. Peripheral chromatin on 
the nuclear wall in the form of granules can sometimes be observed in the 
living condition and generally in the fixed and stained specimens. The 
cytoplasm becomes sharply defined into a non-granular ectoplasm and 
granular endoplasm during the protrusion of pseudopodia. The amoeba 
generally moves by means of one broadly lobose pseudopodium, which 
however, may not be withdrawn before additional ones are formed. There 
is always one large contractile vacuole, augmented frequently by a few 
smaller ones. 
h. Division, Gradually the rapid movement of the granules and of 
the nucleus through the endoplasm becomes slower, the pseudopodium is 
retracted, the granules clump together, then lose their identity so that the 
entire protoplasmic body becomes homogeneously refractive, and thus a 
''gel" state is formed during which the nucleus is obscured (fig. 1, C). 
The animal may remain quiescent in this state for from thirty seconds to 
several minutes, after which it suddenly elongates, constricts in the middle 
and divides into two daughter cells, meanwhile passing from the "gel" 
to the "sol" state (fig. 1, D, D'). The formation of a "gel" state during 
the process of division in higher animals has been noted in many papers by 
a number of observers, among whom are Chambers^ and Heilbrunn.^ 
Multiplication may continue for a number of generations without flagel- 
lation, or the amoeba may pass through a flagellate phase. Finally in 
each case the amoeba becomes encysted. 
3. Flagellate Phase: — (fig. 1, G). Tetramitus varies much in size and 
in form as has been noted by Perty,^ Fresenius,^^ Dallinger and Drysdale,^^ 
Stein, ^2 and Klebs,^^ but the typical form is that described by them as 
"conical" with the pointed end directed posteriorly. The contractile 
vacuole and cytostome are located at the flattened anterior end which 
bears four flagella. The nucleus is slightly posterior to the contractile 
vacuole, and is similar in organization to that of the amoeba just described 
except that it is smaller measuring 3 /x to 5 ^ in diameter. The animal is 
usually 14/x to 18yu in length and 7 /x to 10 m in greatest width. 
4. Transformation of an Amoeba to Tetramitus : — After the amoeba has 
passed through one or more generations by division, some of them may 
transform into flagellates. While the morphological changes may vary 
during the process, the results of one observation will now be given in 
detail. An amoeba retracted its pseudopodium, but changes in outline 
