SURVEY OF UNICELLULAR ANIMALS 



51 



stance, Euglena is an organism that is claimed by both zoologists 

 and botanists: by the former because it can employ complex food 

 materials, and by the latter because in the presence of sunlight it 

 can manufacture its own food. Such forms attest the fact that it 

 is impossible to distinguish sharply the so-called animal and plant 

 kingdoms — one merges into the other when the primitive forms 

 of life are approached. Our classifications fail at the lowest level 



■»■.?■ -H» 



■■• •• • •';>♦ 

 *-•■ • •..-;.•.;.*,♦ 



mm 



I 

 I 



I 



Trachelomonas 



Fig. 23. 



«" 



Peranema 



Bodo 



Phacus Monosiga Trichomonas Cercomonas 



Common flagellated Protozoa (Mastigophora). 



Nucleus 



of life: all living nature is one. Moreover it is not possible to draw 

 a hard and fast line between the Mastigophora and the Sarcodina 

 because certain organisms possess both flagella and pseudopodia 

 during various phases of their life. (Figs. 18, 22, 23.) 



The Mastigophora are very widely distributed in sea, pond, and 

 infusions of organic matter. An immense order, the Dinoflagel- 

 lida, constitutes not a small part of the 

 microscopic life of the sea, competing 

 with the Sarcodina and microscopic 

 plants in variety of species and number 

 of individuals — numbers so immense 

 that wide areas of the sea may become 

 discolored or appear phosphorescent. 

 Others, such as the Trypanosomes, have 

 invaded the field of parasitism, living in 

 the digestive tract and blood stream of 

 higher animals. (Figs. 24, 224.) 



The versatility of the Mastigophora in FlG - 24 -~ A Dinoflagdlate, 

 mode oi lite and nutrition apparently im- 

 plies a high potential of adaptation and evolution. Indeed, it is 

 among them that certain interesting associations, or colonies, of 



Flagella 



