INTRODUCTION. 1 5 



of Algae. Some species, however, prey upon Rotatoria 

 and other microscopic animals. They seem to have a 

 certain selective power ; but this is not universal. It is 

 supposed to be absent from Amoeba and Pelomy., 

 which surround with their pseudopodia, and draw in, 

 whatever comes in their way. In certain of the 

 Vampi/rellae a power of selection is very pronounced. 

 The Reticularia, according to Verworn, normally take 

 in only living organisms. Some of the Heliozoa e. g. 

 Actinospherium 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 Amoeba proteus, which may be taken as typical 

 of the order Amoebina, 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 flowing around it forms a 

 " gastric 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 to it 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 



