540 
Entamoeba giiigivalis 
Such methods may be of service in diagnosing the presence or absence 
of the amoebae in a given preparation but even then their use and value 
is questionable especially if it should happen that the material contains 
only small examples of E. gingivalis. It is absolutely essential, as 
Craig points out, to keep the film moist during the whole of the fixing 
and staining processes if any adequate idea of the structure of the 
organisms is to be obtained. 
We have found iron-haematoxylin to be the most useful stain for 
revealing the detailed structure of the organisms and most of our films 
are stained with this. 
Dobell’s iron-haematein^ is a very good stain which is especially 
useful on account of the rapidity with which it can be used. After 
washing out the fixative the preparation is treated in the mordant, 
1 % ferric ammonium alum in 70 % alcohol for ten minutes. It is 
then rinsed in 70 % alcohol and stained for ten minutes in 1 % hae- 
matein in 70 % alcohol, following which, it is differentiated in the mor¬ 
dant or in acid 70 % alcohol, and finally washed in several changes of 
ordinary 70 % alcohol. By the use of this stain one can quickly obtain 
well-stained preparations presenting clear pictures of the detailed 
structure of the organisms. 
Other stains which we have employed are Jenner’s blood stain, 
Ciemsa’s stain, Unna’s polychrome methylene-blue, safranin and licht- 
grlin, Mann’s methyl-blue eosin, and methyl-green. In using the last- 
mentioned stain we have found it best to fix the preparation in absolute 
alcohol for about ten minutes and then take down through graded 
alcohols to water, after which it is floated on a solution of methyl- 
green in 1 % acetic acid for a minute or so and then mounted on a slide 
in a small quantity of Ripart and Petit’s medium and sealed round 
with marine glue. Since this stain has only been used to investigate 
the nature of the round inclusions within the amoeba and also the 
character of the amoeba nucleus its impermanency is a matter of no 
consequence. 
Morphology. 
(«) The living amoeba. 
We are not in a position to add anything new to the published 
accounts of the structure, appearance, and movements of the living 
amoeba in its ordinary vegetative stage of existence. The recent 
paper by Craig (1916) deals fully and adequately with these matters. 
^ Uobell, C. C. (1914). Cytological studies on three new species of Amoeba. Arch.f. 
Frotist. XXXIII. 143. 
