668 Blackman.—The Primitive Algae 
3. The resting cells are cysts formed vegetatively, and 
zygotes do not occur, as no sexual distinction or reproduction 
occurs in the Flagellata. 
Five subdivisions of the Flagellata are proposed by Klebs. 
I. Protomastigina , including the small simplest forms which 
have only a periplast, are abundantly amoeboid, and always 
colourless. These absorb food either by their whole periphery 
or only at the fore end, where however there is no definite 
mouth. (. Bodo , Fig. 13.) 
II. Polymastigina , larger colourless forms of rather similar 
organization and mostly taking up solid food at definite 
places with a mouth, but this never at the fore end. This 
group has no plant affinities at all. (. Hexamitus , Fig. 13.) 
III. Euglenoidina , large forms with well-developed plasma- 
membrane, ‘ metabolic ’ but never amoeboid. At the fore 
end is a mouth through which the cilia are attached to the 
wall of a vacuole (Wager, ’ 00 ). The body is colourless or with 
green disk chromatophores. The nutrition may be holophytic, 
saprophytic, or animal. (. Euglena , Fig. 13.) 
IV. Chloromonadina , body somewhat amoeboid and without 
plasma-membrane, numerous discoid (yellow-green) chloro- 
plasts. The nutrition is holophytic and division takes place 
in a mucilage-invested resting stage. Only two or three 
genera of this type are known. ( Vacuolaria , Fig. 13.) 
V. Chromomonadina , cells single or in colonies ; structure 
various, no plasma-membrane. Most of the numerous forms 
have one or two brown chromatophores and the nutrition is 
holophytic. 
The last three groups with coloured chromoplasts suggest 
affinities with Algae, and Klebs in 1893 suggested an undefined 
connexion between the two green groups and the Chlamy- 
domonads. The affinity between the Chromomonadina and 
certain groups of brown Algae does not admit of much doubt, 
and the nature of this affinity, on which recent work has thrown 
new light, will be considered in Section V. 
The Euglenoidina are a rather specialized group which 
does not obviously lead to the Chlamydomonad type. The 
