No. 416.] PROTOZOA OF ESPECIAL INTEREST. 651 
Heterophrys, Sphzerastrum, etc., according to such an hypoth- 
esis. In either hypothesis Nuclearia would form an important 
intermediate link. 
Mastigameeba verrucosa S. K. 
A number of specimens of this interesting form appeared in 
one of my cultures during October, and I had a good oppor- 
tunity to study it. The species is different from that described 
by F. E. Schultze (Mastigameba aspera), and belongs appar- 
ently to that which Kent described as M. verrucosa, although 
in size and general form, etc., it agrees with the description of 
Mastigameba invertens of Klebs. I could not make out, how- 
Fic. 2. — Mastigamæba verrucosa S. K. A, spherical form assumed when swimming with the 
ellum in advance; 2, flattened form with lobose pseudopodia. x 1250 
ever, that the organism reverses its axes when it comes to rest, 
— à point upon which Klebs placed considerable importance. 
When first observed this species of Mastigamoeba appears 
like a monad with an irregular outline, which makes its way 
through the water with a peculiar irregular course, vibrating 
the while as though shaken vigorously. The cause of the 
vibration is the action of the rather long flagellum, which is 
directed in advance. On all sides of the minute body are 
lobose processes of variable length (Fig. 2). After pro- 
Sressing in this way for some time it finally comes to rest 
and the pseudopodia are stretched out in all directions, like 
those of a small Amoeba. The flagellum, in the mean time, 
vibrates slowly at one end. In its usual motile condition 
the organism is round, but when quiet and with outstretched 
