MASTIGOPHORA 25 



and strands. The colony is in some cases very complex with division 

 of labor among the different individuals. 



The Mastigopliora have been known from the earliest period of 

 the study of microscopical animals under the general name of Flagcllata, 

 and are still so known in many textbooks. The name Mastigopliora 

 was given the group by Biitschli in 1883. The animals live in both 

 fresh and salt water, and many are parasites in the higher animals, 

 being often the cause of disease. Large numbers closely resemble 

 plants and many are on the border line between animals and plants. The 

 class contains 3 subclasses with about 350 species. 



Key to the subclasses of Mastigopliora: 



Oi Small Mastigophora with a definite anterior and posterior end, at one or the 

 other of which are 1 or more fiagella 1. Flagellidia 



a^ Mastigophora with usually 2 fiagella, 1 anterior and 1 transverse in posi- 

 tion 2. DiNOFLAGELODIA 



O3 Large marine Mastigophora with parenchymatous protoplasm. 



3. Cystoflagellidia 



Subclass 1. FLAGELLIDIA. 



Body with a well-defined cuticula which gives it a definite shape, 

 the cuticula in some forms, however, being so thin that changes in shape 

 often take place; pseudopodia formed in certain forms; many flagel- 

 lates are protected by external coverings of jelly, chitin, silica or 

 cellulose; 1, 2 or several fiagella extend fi'om one end of the body, 

 usually the forward; in the Clioanoflagellida, however, the single flagel- 

 lum is at the hinder end and is surrounded at its base by a collar: 8 

 orders, in which are included the great majority of flagellates, very 

 many containing chromatophores and being apparently allied to plants. 



Key to the orders of Flagellidia: 



fli Body colorless, often more or less amoeboid, and with one or more fiagella. 

 6i Body spiral with or without fiagellum, and more or less like bacteria. 



1. Spirochetida 

 &2 Body not spiral. 



Ci One fiagellum with collar present 3. Choanoflagellida 



C2 No collar present, 

 di Body with indistinct cuticula, often more or less amoeboid. 



Ci Body elongate with undulating membrane 5. Tbypanosomatida 



€2 No undulative membrane present, 

 /i Two or more fiagella, one directed forward, the other trailed behind. 



4. Heteromastigida 

 /o Fiagella always directed forward. 



g^ One or two fiagella ; body usually more or less amoeboid. .2. Monadida 



g. Three or more fiagella 6. Polymastigtda 



(/, Body with distinct cuticula 7. Euglenida 



fla Body usually either yellow or green, often colonial. 



61 Body with distinct cuticula, and usually solitary 7. Euglenida 



62 Body usually with a hyaline, gelatinous or cellulose house ; colonial, 



8, Piiytoflagellida 



