112 JOURNAL OF SCIENCE. 
duced into remarkable horn-like processes, which are charac- 
teristic of particular genera. 
Except in three genera, the body is provided with an 
exoskeleton, in the form of a membrane, which may be either 
structureless or variously ornamented. On the ventral aspect 
there is, in such genera, either a large aperture or a longitudinal 
slit in the membrane, through which the protoplasm comes 
into direct contact with the exterior. There is also usually a 
transverse groove through apertures in which the cilia are 
protruded. 
But the point of chief interest in the skeleton is its chemical 
composition. Bergh has succeeded in proving, by numerous 
chemical tests applied. to a large number of species, that the 
membrane consists of cellulose, or at any rate of some very 
similar carbo-hydrate. This, I believe, is the first time that 
cellulose has been actually demonstrated in the cell-wall of the 
Protozoa; the only case in which that substance has hitherto 
been known in the animal kingdom being that of the Tunicata. 
Equally important are the results of the investigation of the 
contained protoplasm of these organisms. It is usually divided 
into ectoplasm and entoplasm, the latter of which is found to con- 
tain chlorophyll,diatomin (the yellowish-brown colouring matter of 
diatoms), and starch. Chenophyll is already known to occur in 
many animals of widely-separated groups, starch has hitherto 
been proved to exist only in the green Turbellarians, and 
diatomin has never before been known out of the vegetable 
kingdom. 
Professor Huxley says, speaking of the differences between 
animals and plants,* “The most characteristic morphological 
peculiarity of the plant is the investment of each of its com- 
ponent cells by a sac, the walls of which contain cellulose or 
some closely analogous compound ; and the most characteristic 
physiological peculiarity of the plant is its power of manufac- 
turing protein from chemical compounds of a less complex 
nature. The most characteristic morphological peculiarity of 
the animal is the absence of any such cellulose investment. The 
most characteristic physiological peculiarity of the animal is its 
want of power to manufacture protein out of simpler com- 
pounds.” 
It will be seen that both these distinctions break down in the 
case of the cilio-flagellata; their cell-wall is proved—as Huxley 
suggested might be the case, in a note to the passage just 
quoted—to be practically identical with that of plants, and the 
presence of starch proves clearly that the chlorophyll has the 
same function as that of plants, the decomposition of the car- 
bonic acid in the surrounding medium. Bergh, indeed, believes 
that in many genera the nutrition is entirely like that of a 
plant, and that no solid nutriment is ever taken up; and great 
weight must be attached to an opinion founded on so many 
* « Anatomy of Invert. Animals,” p. 45. 
