OMNIVOROUS ECHINODERMS, &c. 



269 



bent back so as to make a kink or bend in the filament. By 

 a continuance of this sort of manoeuvring the animalcule often 

 succeeds in coiling up the alga into a compact mass of con- 

 venient shape, adapted for easy digestion. In briefly dealing 

 with human anatomy and physiology it was pointed out (vol. i, 

 p. 39) that the circulatory fluids of the body, blood and lymph, 

 contain innumerable microscopic bodies, the white corpuscles, 

 which progress by creeping movements, in the same way as just 



Fig. 472. A Proteus Animalcule (Amoeba} surrounding a slender alga. The numbers fi-8) 

 indicate the successive stages in the process. Much enlarged. 



described for the Proteus Animalcule. Nor does the resemblance 

 between the two stop here, for the white corpuscles feed by taking 

 in particles bodily, a fact of great importance, and one which has 

 caused them to receive the name of "eating-cells " (phagocytes 

 Gk. phagein, to eat; cytos, a small box, hence a cell). The white 

 corpuscles, indeed, play a very important part in most if not all 

 groups higher in the scale than Protozoa, for they perform the 

 functions of scavengers and police. In human beings, for example, 

 they attack and devour disease -germs which have made their way 

 into the system, and the upshot of many cases of infectious dis- 

 ease depends upon the result of a vigorous contest between cor- 

 puscles on the one hand and germs on the other. 



Some very interesting freshwater Rhizopods are practically 

 amoebae provided with shells, and a shell-bearing group some- 

 what more distantly related is that of the Foraminifera, members 

 of which abound in the sea, and are also found to a less extent 



