PEOTOZOA 5 



way. There is reason to believe that in some species one 

 part of the periphery may be specially endowed as a sort of 

 mouth region. But what happens is that, when the diatom 

 or other food has been encountered by the pseudopodium or 

 pseudopodia, it is gradually surrounded by pseudopodial out- 

 growths, which, fusing together, bring about the lodgment of 

 the food in the endoplasm ; this is ingestion. The food is now 

 surrounded by endoplasm which secretes a watery fluid into 

 the space occupied by the food, and if watched long enough the 

 food will be found to be killed, broken up, and gradually dis- 

 solved. The undigested remains are got rid of by a reverse 

 process which brings 

 them to the surface ; 

 this is egestion. 



The individual cell 

 is thus able to move 

 about, to take in solid 

 food and digest it ; it 

 is, in fact, able to live 

 by the performance in 

 a simple fashion of the 



FIG. 2. Diagram of the movement of an 

 Amoeba, after Jennings. The upper figure 

 indicates the relative rate of the granules 

 and ectoplasm in the Amoeba and in the 

 pseudopodia. The lower figure represents 

 the path of a point on the surface. 



ordinary physiological 

 processes known to be 

 essential to life. 



^Reproduction is very simple. The cell elongates, the 

 nucleus divides into two nuclei, and these are carried apart in 

 the elongating cytoplasm, which at the same time becomes 

 constricted between them. The two halves finally become 

 separated and two Amoebae are produced, each half the size 

 of the original. In fresh-water conditions a new contractile 

 vacuole appears in one of the daughter cells. These cells then 

 proceed to feed and grow to the full size, when the process is 

 repeated. The rate of growth and reproduction is influenced 

 by temperature. Both processes are rapid in high tempera- 

 tures and gradually become slower in decreasing conditions of 

 temperature. Thus in temperate climates reproduction and 

 growth are subject to a winter stasis from which there is a 

 gradual change to a summer maximum of intensity. 



After a period of multiplication it is believed, although it 



