MORPHOLOGY AND TAXONOMY OF THE MASTIGOPHORA 421 



SPECIFIC CLASSIFICATION. 



1. The Water- dwelling Flagellates. — In separating the chloro- 

 phyll-bearing flagellates from Protozoa we encounter the difficulty 

 of border-line forms which, except for the absence of chlorophyll, 

 appear to be related to forms with chlorophyll. Euglena gracilis, 

 for example, ordinarily has chlorophyll, but upon cultivation in the 

 dark the chlorophyll is lost and the organisms live as saprophytes. 

 Such forms combine, therefore, holophytic and saprophytic modes 

 of food-getting, but it is obvious that they should not be included 

 with animal flagellates. By the same reasoning a number of 

 colorless forms should be retained with their structurally similar 

 colored relations so long as there is no question regarding their 

 homologous structures. Thus the colorless Chilomonas is so similar 

 to Cryptomonas in structure that it may be regarded as a descen- 

 dant of a chlorophyll-bearing form which has become permanently 

 adapted to a saprophytic mode of life. So, too, many of the Dino- 

 flagellates have lost their chlorophyll and live as animals do, either 

 by holozoic methods (Gymnodinium, Xoctiluca, etc.) or by parasitic 

 methods (Oodinium, Haplozoon, etc.). Here the characteristic 

 structures of the Dinoflagellates in swarm spores or adults are so 

 pronounced that the affinities are clearly indicated. 



With other colorless flagellates, however, which have been 

 claimed by botanists, the affinities are obscure and there is no more 

 reason for regarding them as recently modified chlorophyll-bearing 

 types than as definitive animals. It may be true that all animal 

 groups should look back to the dim past for their plant ancestors, 

 but this does not mean that modern zoology should continue to 

 rest in the lap of botany. 



Among such colorless forms which should be transferred to the 

 animal flagellates, Astasia, Menoidium, Englenopsis, Peranema, 

 Urceolus and Petalomonas would be classified as Protomonads; 

 Distigma, Sphenomonas as Monadidae; Heteronema, Tropido- 

 scyphus, Anisonema, Entosiphon and Marsupiogaster as Bodonidae. 

 These are all free-living holozoic or saprozoic forms living in fresh, 

 salt and brackish waters. 



CLASSIFICATION OF THE ANIMAL FLAGELLATES. 



Phylum Protozoa, Goldfuss, 1820. 



Sub-phylum Zoomastigophora (Animal Flagellata). 



Class I. Protomastigota. 

 Order 1. Protomonadida. 



Family 1. Rhizomastigidae. 

 Family 2. Oicomonadidae. 



