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77/ E . I ME R ICA X X. I TV H . 1 L IS 7 



[Vol. LIV 



Ordee Heteromastigida 

 Genera: Elvirea 



Dinomonas 

 Pleuromonas 

 Spiromonas 

 Order Phytomastigida 

 Genera : Amphimonas 

 Heocamita 

 Order Euglenida 



Genera : Crypt oglena 

 ■ . Notosolenus 



Almost all the mastigophora, but more especially the 

 minute forms, vary in size and shape within the limits of 

 the species. Individuals of apparently the same species 

 are often found half, and even a fourth, of the size which 

 is normal for that species, while abnormally large forms 

 are more rarely encountered. It is the smaller forms 

 which are the most puzzling. These are probably due 

 to: (1) the div ision of the adults, for binary fission along 

 the line of the antero-posterior axis is the prevailing 

 mode of reproduction among the Mastigophora. "Where 

 division is occurring rapidly, in a crowded culture many 

 such forms will be found. Often the young again sub- 

 divide, even before reaching adult proportions. This 

 gives rise to individuals of a species varying widely in 

 size, (2) to the fact that the adults themselves vary in 

 size, even where division is not rapidly taking place, and 

 (3) to the possible production in some forms of swarm 

 spores. Possibly when the life histories of a greater 

 number of the smaller flagellates become known, it will 

 be found that many species multiply not only by binary 



without the cyst. It is not unusual to li„d individuals of 

 a colonial form which have freed themselves, or have 

 been broken away, from the parent community, and 

 which are, temporarily, at least, living an independent 



