MORPHOLOGY AND TAXONOMY OF MASTIGOPHORA 253 



it was superseded by the more natural classification of Pascher and 

 Lemmermann (1912) which, in the main, is adopted here. 



The chlorophyll-bearing forms are fairly homogenous and together 

 with the colorless forms which by reason of their structures and life 

 histories belong with them, form a large division of the Mastigo- 

 phora. Other colorless forms, not obviously related to chloro- 

 phyll-bearing types, form a second large division. These two divi- 

 sions are given the value of classes in the present work and with 

 their subdivisions will be considered in accordance with the following 

 classification : 



Sub-Phylum Mastigophora, Diesing. 



Class I. Phytomastigoda (Phytomastigina of Doflein) 



Chrysomonadida 

 Cryptomonadida 

 Dinoflagellida 

 Phytomonadida 

 Euglenida 

 Chloromonadida 

 Class II. Zoomastigoda (Zoomastigina, Doflein) 

 Order VII. Pantastomatida 

 Order VIII. Protomastigida 

 Order IX. Polymastigida 

 Order X. Hypermastigida 



Class I. PHYTOMASTIGODA. Doflein em. 



In this group of Mastigophora are included not only the flagel- 

 lated forms which by virtue of their chlorophyll are able to live in 

 a typical autotrophic manner, but also those forms which, although 

 they are colorless, nevertheless by their structures and life histories 

 show unmistakable relationship to the chlorophyll-bearing flagel- 

 lates. It cannot be claimed that the arrangement of orders within 

 the class represents an ascending scale in complexity of structures 

 or functions. Each order includes some forms which are relatively 

 simple, others complex, in regard to nuclear and kinetic structures, 

 vacuole system, and cell membrane. In two orders only, the 

 Euglenida and the Chloromonadida, are the genera all of a higher 

 type of organization, while the Phytomonadida, with obligatory 

 autotrophic nutrition, are much more advanced in respect to sex 

 dift'erentiations than are the representatives of other orders. 



Many of the phytomastigote flagellates are extremely small 

 (2 to 4 ;u), but the great majority measure from 25 to 100 ju in length, 

 while some exceptional types are relatively large, Nodiluca miliaris, 

 for example, with a diameter of 1 to 1.5 mm. 



The typical form assumed is monaxial and ellipsoidal, but there 

 are wide variations. Many are polymorphic, passing from sym- 



