AMCEBA AND SOME ALLIES 



295 



In conjugation two paramecia unite temporarily in the 

 manner indicated in the figure. A fraction of the micro- 

 nucleus of each passes through the two contiguous layers of 

 ectoplasm and unites with a similar fraction in the other 

 animal. When this and certain other less essential phenom- 

 ena have taken place, the individuals 

 separate and continue the process of 

 transverse division, but with greater 

 frequency than before. Professor L. 

 L. Woodruff of Yale University has 

 found that conjugation is not neces- 

 sary to the life of Paramecium. By 

 isolating single specimens of Parame- 

 cium he kept watch so that each time 

 the animal divided the parts were 

 separated. In this manner conjuga- 

 tion was entirely avoided for ten 

 years. During this time there were 

 twelve thousand generations. Since 

 the animals showed no ill effects we 

 must conclude that Paramecium can 

 continue to reproduce indefinitely 

 without conjugation. 



The Malarial Parasite. Many one- 

 celled animals are parasitic. One of 

 the most studied in recent years is one 

 of the malarial parasites of man (Plas- 



mo'&ium mala'rix, Fig. 155). There are several different 

 species of malarial parasite. These differ one from another 

 in appearance and in the nature of the diseases which they 

 produce. While the most generally known species cause 

 human malaria, other species live in birds and in other ani- 

 mals. The life history of these organisms is so long and com- 

 plicated that we can give but a brief account of it here. 



Fig. 154. Paramecia con- 

 jugating. (Much en- 

 larged) 



After Saville Kent 



