332 MASTIGOPHORA AND PROTOMONADINA 



A. Body inflated with gelatinous substance — -Subclass i, Cysto- 



flagellata Haeckel, 1873. 



B. Body not so inflated : — 



I. Periplast markedly thickened, with two flagella arising 

 in the middle of the body, one trailing and one lying 

 in the transverse groove — Subclass 2, Dinoflagellata 

 Biitschli, 1885. 

 II. Periplast thin, with a variable number and arrangement 

 of flagella — Subclass 3, Euflagellata Cohn, 1887. 



Only the third subclass concerns us. 



SUBCLASS EUFLAGELLATA Cohn, 1887. 



Definition. — Mastigophora without body inflated with gelatinous 

 substance, and possessing a thin periplast and a variable number 

 and arrangement of flagella. 



Classification.— The Euflagellata may be classified into orders as 

 follows: — 



A. Chromatophores often present :~ 



I. With cellulose envelope — Order i, Phytomonadina 



Blochmann, 1895. 

 XL Without cellulose envelope — 



A. Small forms without oesophagus or vacuole system 



— Order 2, Chromomonadina Klebs, 1872. 



B . Large forms with oesophagus and vacuole system — 



Order 3, Euglenoidina Biitschli, 1884. 



B. Chromatophores absent : — 



I. Amoeboid forms in which the food is captured by 

 ' • kd^ & pseudopodia- — Order 4, Rhizomastigina Biitschli, 

 1884. 



II. Non-amoeboid forms in which the food is usually 

 captured by flagella^ — Order 5, Protomonadina Bloch- 

 mann, 1895. 



We are only concerned with Order 5, Protomonadina. 



ORDER V. PROTOMONADINA Blochmann, 1895. 



Definition.— Euflagellata in which chromatophores are absent and 

 in which tlie individuals are non-amoeboid and usually capture their 

 food by flagella. 



Remarks. — As defined above, the Protomonadina is a large order, 

 and includes the Polymastigina of Biitschli and Blochmann, as well 

 as the Binucleata of Hartmann, both of which were treated as 

 separate orders in our previous editions. We, however, fore- 

 shadowed a return to Doflein's method of classification, and dis- 

 cussed the whole subject on pp. 282 and 283 of the second edition. 



Classification. — ^So large is this order that, for convenience' sake 

 as well as for morphological reasons, it may advantageously be 



