652 THE AMERICAN NATURALIST. [VOL. XXXV. 
pseudopodia it assumes a flattened shape, and a distinct ecto- 
plasm and endoplasm can be made out. After a shorter or 
longer period of rest the action of the flagellum becomes 
more and more rapid, the body becomes detached from the 
substratum and assumes a spherical form, after which it 
again moves through the water with the peculiar vibrating 
motion which first attracted my attention. A minute con- 
tractile vacuole pulsates at irregular intervals and cannot be 
made out easily when the organism is moving. A small 
spherical nucleus lies near the base of the flagellum, but no 
structure could be made out. 
In the resting condition the pseudopodia surround and take 
into the body small objects of different kinds, which are stored 
up in the endoplasm until digested. The process is apparently 
no different from that in Ame@ba proteus. 
Mastigameeba belongs to a group of flagellated amoeboid 
forms, the Rhizomastigide which Bütschli regarded as ances- 
tral to both flagellates and rhizopods. Klebs, on the other 
hand, placed the beginnings of both groups farther back, and 
considered the Rhizomastigidze as flagellates which have become 
amoeboid. 
Multicilia 
Only one individual of this interesting genus was seen, and 
no details were made out save the presence of about twenty 
long flagella-like cilia distributed evenly about the body. By 
means of these appendages the organism moved along with a 
rolling motion. 
The search for the beginnings of the ciliate stem from some 
more generalized organisms has been singularly vain. The con- 
servative structure which the infusorian body presents gives 
but little clue to their ancestry. In only one other known case 
(Polykrikos among the Dinoflagellidia) is there a similar nuclear 
dimorphism, while the almost universal reproduction by trans- 
verse division is met with among the Mastigophora but rarely. 
It is generally conceded that the infusorian stem must have 
arisen from the flagellate stem at an early period, and must 
have become progressively differentiated until the present 
"EE 
xo T 
