Unicellular Animals Protozoa. 75 



by fission is common here also, as in the case of Protococcns, 

 although in Amoeba no cellulose cell-wall is formed. As in 

 Protococcus so in Amoeba, division of the nucleus precedes 

 division of the mass as a whole. 



Anmba is an animal because it possesses no cellulose 

 cell-wall ; because chlorophyll is absent ; and because the 

 organism is for that reason incapable of using the carbonic 

 acid of the atmosphere and the water and simple salts of 

 the soil in the manufacture of new protoplasm, but requires 

 to be supplied with organised matter or protoplasm already 

 partially or entirely integrated. 



As regards its physiology, it is to be noted (p. 35) that 

 carbonic acid is constantly being produced, both in the dark 

 and in sunlight, and thus it presents superficially a great 

 difference to the plant where carbonic acid is exhaled in 

 quantity in the dark only, whilst in daylight its exhalation 

 is masked by the comparatively large amount of oxygen 

 given forth contemporaneously. 



