CLASSIFICATION OF THE MASTIGOPHORA 49 



Order 1. Adinida. Dinoflagellates -n-ithout furrows, the two flagella free in the 



water, the transverse with movement the same as though the furrow were 



present. 

 Typical genera: Prorocentrum, Ehr., 1S33; Exuviella, Cienk., 1882. 

 •Order 2. Diniferida. Dinoflagellates ■with furrows, one transverse, the other 



longitudinal. 

 Family 1. Peridinidw. The transverse furrow is without wide ledges and the 



shell may be absent. 

 Typical genera: Peridinium, Ehr., 18.32; Ceratium, Schrank, 1793; Gleno- 



dinium, Ehr., 1835; Gymnodinium, Stein, 1878. 

 Family 2. Dinophysidw. The borders of the cross furrow are developed into 



great ledges, making a deep furrow for the flagellum. 

 Typical genera: Dinophysis, Ehr., 18.39; Cithiristes, Stein, 1883; Amphidinium, 



Clap, and Lach., 18.59; Ceratocorys, Stein, 1883; Triposolenia, Kofoid, 1906. 

 Order 3. Pol^tdixida. The order consists of but one genus, Polykrikos, Biitschli, 



1873, which is characterized Iw a naked body, by several transverse furrows 



and flagella, by macro- and micronuclei, and nematocysts. 

 Subclass 3. Cystoflagellata. Marine protozoa, which are plant-like in having a 



highly parenchymatous body, a single nucleus and a firm membrane. The 



young forms pass through a dinoflagellate stage in development. 

 Three genera: Noctiluca, Surirav, 183(3; Leptodiscus, Hertwig, 1877; Craspe- 



dotella, Kofoid, 1905. 



Cilia, and Classification of the Infusoria. — Cilia are quite differ- 

 ent from flagella, being .shorter and moving with a sharp stroke in 

 one direction and with a slower, non-forceful recover}^ in the opposite 

 direction. Like the flagellum, the cilium is thicker at the base and 

 tapers to a fine point, while it owes its contractility to the presence of a 



Fig. 17 



Aspidisca hexeris, Quea. An hypotriclious ciiiate with bru.:ihes of fu.sed cilia. 

 (After Calkins.) 



filament of kinetic granules placed along one edge of the cilium, the 

 contraction of this thread furnishing the power of the cilium, while 

 the synchronous contraction of thousands of similar cilia furnishes 

 the motive power of the organism. 



In some forms, as in ilileptus or paramecium, and the majority of 

 4 



