INTRODUCTION. 15 
of Algee. Some species, however, prey upon Rotatoria 
and other microscopic animals. They seem to have a 
certain selective power ; but thisis not universal. It is 
supposed to be absent from Amaba and Pelomywa, 
which surround with their pseudopodia, and draw in, 
whatever comes in their way. In certain of the 
Vampyrelle a power of selection is very pronounced. 
The Reticularia, according to Verworn, normally take 
in only living organisms. Some of the Heliozoa—e. 9. 
Actinosphertwm—capture both infusorians and rotifers, 
but their staple food, like that of the Rhizopoda in 
general, is chlorophyll, derived from the sources already 
mentioned. 
In Ameba proteus, which may be taken as typical 
of the order Amcebina, food, of whatever kind, may be 
incepted at any convenient part of the body-surface. 
A pseudopodium is directed towards the object encoun- 
tered—say a diatom—and flowimg around it forms a 
“oastric vacuole.” In this the diatom remains until 
digestion is completed. Finally, the siliceous frustule, 
deprived of its chlorophyll, is ejected. The chloro- 
phyll, from whatever source derived, is seen rolled into 
balls or pellets and scattered through the endoplasm, 
giving toit a more or less green tinge. The water, 
entering the gastric vacuole along with the food, is 
believed to change gradually by osmosis with the 
fluids of the plasm. These contain a digestive acid 
which reduces the digestible portions of the food 
probably to some form of peptone, and this, again 
by osmosis, is then assimilated in all parts of the 
endoplasm. 
A remarkable similarity has been found to exist 
between the action of the naked Lobosa and certain 
fluid substances, and upon this some ingenious theories 
have been constructed. Rhumbler, in 1898, following 
suggestions and experiments made previously by Hofer 
and others, demonstrated that a drop of chloroform 
will attract a shellac thread from the surrounding 
water and roll it up within its substance, just as an 
