72 Universitij of Calif ornia Publications in Zoology . [Vol. 16 



as a generic character, unless this has so modified the structure of the 

 organism that it has also become morphologically differentiated and 

 significant. The ability to live in one medium rather than another, 

 as in fresh water or the intestinal fluid, is dependent on chemical 

 reactions and differences, and is often acquired as a secondary modi- 

 fication, as shown in the possibility of both free and parasitic life by 

 the same organism, as in the case of trichomonad flagellates (Kofoid 

 and Swezy, 19156). 



Alexeieff has added more confusion to the already existing chaos. 

 In describing the flagellate from Motella tricirrata and M. mustela he 

 (1910) uses Moroff 's name, Vrophagus, rejecting Hexamitus, "parce 

 qu'il esprime un caractere base sur une observation inexaete (en 

 realite il y a 8 flagelles)." In 1911 Alexeieff describes the same or a 

 similar flagellate from species of Triton and A.rolotl and designates it 

 as Octomitns intestinalis Prow, without reference to his previous ac- 

 ceptance of the name Vrophagus intestinalis Moroff. Again in 1912 

 he figures Hexamitus parvus Alex. {"H. intestinalis Du.j. pro parte = 

 Ocfomitus dujardini Dobell pro parte"), and gives no reason for 

 using a name which he had previoiLsly discarded. In 1914 he says, 

 " Contrairement a 1 'opinion de Dobell et de ]\Iinchin on ne pent pas, 

 pour agir conformement aux regies de la nomenclature, changer le 

 nom Hexamitus pour I'Octomitus, malgre que 'Hexamitus' consacre 

 une erreur d'observation (en realite il y 8 flagelles et non 6)," and in 

 the following paragraph gives both Hexamitus and Octomitus as two 

 good genera of the family Hexamitidae. 



In view of the fact that habitat alone cannot be used as a generic 

 character, and that all the species thus far described are morpholog- 

 ically similar, different at the most only in specific characters, it is 

 evident that the name Octomitus must be discarded in favor of the 

 older term Hexamitus. That inaccurate observation was the basis of 

 the first description and generic designation cannot be given as a 

 reason for discarding the original generic name, as applicability from 

 the standpoint of description is not a basis for testing the validity of 

 generic names. This principle, if adopted, would throw out many 

 generic names from the list of protozoan genera. 



For these reasons we use, on the grounds of priority, as the generic 

 name for the eight-flagellated protozoan, both parasitic and free-living, 

 Hexamitus Du.jardin, recognizing as the type species H. inflatus 

 Dujardin, the first species in Du.iardin's (1841) paper. 



