MANUAL OF ELEMENTARY ZOOLOGY 



regard the ectoplasm and endoplasm as tissues unprovided 

 with special nuclei. In many points of structure and 

 behaviour Ammba resembles closely the white corpuscles 

 of the frog and more distantly the 

 other cells of the frog's body. It is, 

 in short, a self-contained mass of pro- 

 toplasm with a nucleus — an isolated 

 energid. For this reason it has been 

 usual to regard it as a cell, and to call 

 it a unicellular organism, and a theory 

 known as the cell theory is widely held, 

 on which the body of such an animal 

 as the frog is said to be a colony of 

 units, each comparable to a single 

 Amxba, specialised for co-operation 

 with the other cells of the body. But 

 ... f this theory is in reality an inversion 



Ae 74 rektion ofg^rm of the facts. Amoeba is a complete 

 and body substance and independent organism comparable 

 in the frog. The with the whole body of the frog. Its 

 dark circles represent small s j ze ena bles all the functions 

 fksTody cells The which the nucleoplasm performs to be 

 germ gives rise in carried out by a single nucleus. In 

 each generation to the frog the size of the body makes 

 numerous body cells ne cessary a large number of separate 

 ge'her a'nTTven^ nuclei, and around each of these a 

 ally die, and also to part of the cytoplasm is more or less 

 germs (of which only clearly segregated so that an energid 

 one is shown in each ( p _ g 4 ) j s i so i a ted. Such an energid 

 le e r n ms r reav^LbIS i^ted within the body is called a 

 and give rise each to cell. Now the energids which are thus 

 a new group of body isolated as cells have not, as Ammba 

 cells and new germs. jj aSj a n tne properties possessed by 

 L" fmlS the body as a whole, but they have 

 the body substance special qualities according to the 

 mortal. functions which their position in the 



body demands. A cell is a portion 

 of the body of a whole organism which has become special- 

 ised for the performance of particular functions, not, as the 

 cell theory supposes, a whole organism which co-operates 

 with other such organisms to form a body of a higher grade. 



