Vol.. 8, 1922 
ZOOLOGY: M. BUNTING 
295 
In these cultures differences among the active amoebae as well as three 
types of cysts and the flagellate were noted, hence pure lines were started 
by the isolation method. Pure lines derived from culture 10 were desig- 
nated G., I., J. and L.; of these G. and L. are of more special interest, 
the former being obtained from a single specimen of Tetramitus, the latter 
from a smooth, thin-walled cyst. 
The cysts of cultures G. and L. revealed no microscopic differences 
either in the living or in the fixed and stained condition, and when trans- 
plants were made of the cysts in favorable media both active amoebae 
of limax type and Tetramitus developed. Pure lines started from an iso- 
lated amoeba, an isolated flagellate or an isolated cyst in liquid or semi- 
liquid media at room temperature have always given the same results, i.e., 
smooth, thin- walled cysts, the active amoeba of limax type and Tetra- 
mitus rostratus. 
Although the amoeba with the Tetramitus stage was obtained in cul- 
tures from the coecal contents of the rat, the presence of contractile vacuoles 
etc., indicated that this amoeba was not a parasite but belonged to the 
coprozoic protozoa as defined by Dobell and O'Connor.^ Feeding experi- 
ments upon rats and mice were conducted to determine whether the amoeba 
and flagellate stages are present either in the small intestine or in the 
coecum of these animals. Prior to feeding these experimental animals 
their faeces was collected on filter paper and cultures made in liquid media; 
in a few cases the amoeba and tetramitus stage was already present. The 
nine rats and four mice used were killed and opened in one, two, three, 
and five days after feeding and microscopic examination made of the 
fresh contents of the coecum and small intestine. Neither active amoebae 
nor Tetramitus were found, but cysts, both degenerate and normal, were 
present in all the animals. Cultures were made of coecal contents in ster- 
ile liquid media which were studied the following day. The active amoeba 
of the type used in the feeding and Tetramitus were found in these cultures. 
The results of the feeding experiments indicate that the amoeba under 
cultivation belongs to the coprozoic Protozoa. 
Much evidence that Tetramitus is a stage in the life histor}^ of this 
coprozoic amoeba was obtained from the study of the living animal and 
from fixed and stained cover glass preparations, yet to affirm this fact with 
certainty, many consecutive hours of many days have been spent in close 
observation. Much of this study has been conducted on hanging drops, 
made either from a single cyst isolated and placed in a drop of fresh liquid 
medium or a few cysts taken by a platinum loop from a culture containing 
only cysts and adding from two to three loops of fresh medium. All 
were placed on depression slides and ringed with hard vaseline. By this 
method the animals have been kept under observation during the entire 
