80 C. CLIFFORD DOBELL. 
recting for the thickness of the coverslip by means of the 
correction-collar. For permanent preparations I used Zeiss’s 
38 mm. apochromatic oil-immersion (apert. 1°40), or less 
frequently the 2 mm. (apert. 1:40). Compensating oculars 
2, 6,12, and 18 were employed. I used a large Zeiss stand 
and artificial (incandescent) light. 
I have always attached the greatest importance to the 
observations made on the living animal, stained preparations 
being used to check and amplify these observations, 
Culture.—In a state of nature the frog usually deposits its 
feeces in the water or on damp earth. They must, therefore, 
be frequently diluted with water, so that a watery solution of 
the faeces is probably a normal medium for the monad. I 
attempted, however, to discover whether the monads could 
live in other culture-media. Unfortunately, I have not made 
an extended series of experiments in this direction, nor have 
I been able to discover any other natural habitat of the 
monad than that already recorded. I have succeeded, 
nevertheless, in keeping the monads for several days in a 
state of activity and frequent division in organic infusions of 
several kinds, and infusions of faces of several different 
mammals and cf a snake. An organism described as a 
‘“zoospore”? was observed in infusions of cow-dung by 
Cunningham (11) in India. It bears some resemblance to 
my monad when seen under a low power. 
SYSTEMATIC. 
It is not possible at present, owing to our ignorance of the 
life-histories of most flagellates, to assign this form to any very 
definite systematic position. Beyond doubt it belongs to the 
class Mastigophora, Diesing, and to the sub-class 
Flagellata (Cohn) Biitschli. From the morphology of the 
adult form it may further be referred to the order 
Kuglenoidina, Klebs. So little is known of the various 
members of this order that it is difficult to decide upon the 
right family, sub-family, etc., which should include the form 
