THE MASTIGOPHORA 163 



The six sub-classes of Mastigophora may be tabulated as 

 follows : 



Sub-Class 1. Lissoflagellata ) -,-, a ,, , 



, > Luflasjellata. 



2. Choanoflagellata j 



3. Phytoflagellata (Volvocaceae). 



4. Dinoflagellata (Peridiniales). 



,, 5. Cystoflagellata. 



,, 6. Silicoflagellata. 



The Euflagellata are defined as Protozoa which possess a sharply 

 defined, uninuclear sarcode, whose periplast is either a simple 

 ectoplasm or a definite pellicle. During the greater portion of 

 their life they are in motion, or at least capable of motion. They 

 have a definite anterior end, from which one, two, or many flagella 

 arise, and they possess one contractile vacuole or several. Repro- 

 duction takes place by simple longitudinal fission, 1 generally in the 

 flagellate condition, sometimes in a resting condition. It seems 

 probable that most of the Euflagellata are capable of forming 

 resistent cysts, usually called sporocysts. 



The occurrence of a process of conjugation was asserted by 

 Dallinger and Drysdale and others of the earlier observers, but 

 some doubt was thrown upon the accuracy of these statements by 

 Biitschli and Senn. In recent years, however, the formation of 

 definite gametes and a process of conjugation have been proved 

 to occur in Mastigella by Goldschmidt (4), in Pseudospora by 

 Kobertson (18), in Monas and Bodo by von Prowazek (16), in 

 Copromas by Dobell (3), and in Trypanosoma and other forms by 

 Schaudinn (19). There seems to be little doubt, therefore, that 

 conjugation is a normal process in the life-history of all the 

 Euflagellata. 



SUB-CLASS I. LISSOFLAGELLATA, Lankester. 



The members of this sub-class are distinguished from the other 

 Euflagellata by the absence of a collar. The sub -class is divided 

 into the three orders : 



1. Monadidea. 



2. Euglenoidea. 



3. Chromomonadidea. 



ORDER 1. Monadidea, Biitschli. 



The Monadidea comprise the least differentiated forms of 

 Mastigophora, and include genera that exhibit affinities with the 

 Proteomyxa (Multicilia, Pseudospora, p. 8), with the Lobosa (Rhizo- 



1 Cases of true transverse fission are very rare among the Lisso- and Choano- 

 flagellates ; e.g. Oxyrrhis, Stylochrysalis, Phalansterium. 



