266 BIOLOGY OF THE PROTOZOA 



In some cases these are numerous, small, and discoidal in form; in 

 other cases there are only one or two in the cell in which case they 

 are cup-shape or band-form and laterally placed. The exact nature 

 of the coloring matter is unknown but is generally supposed to be 

 the same as that of the Dinoflagellida. Stigmata in the vicinity 

 of the fiagellum-base are common. One or more globular pyrenoids 

 usually enclosed in a shell of amyloid substance, are.likewise widely 

 distributed. Trichocyst-like rods in the anterior end, are found in 

 several types, from which on treatment with reagents, gelatinous 

 filaments are thrown out. The nature of these structures and their 

 functions, are entirely unknown. One or two simple contractile 

 vacuoles are present in the majority of forms and are situated in 

 the anterior part of the dorsal side and empty into the cytopharynx. 



Longitudinal division occurs usually in the motile stage although 

 it takes place in some cases during resting phases. Palmella-like 

 gelatinous aggregates are characteristic of some forms; such a phase 

 is dominant in one famil\' ( Phieocapsidte) where the aggregates 

 take the form of simple or branched threads. Swarmers having the 

 characteristic cryptomonad structure leave the aggregates for pur- 

 poses of reproduction. Sexual processes are entirely unknown. 



Nutrition may be either autotrophic or heterotrophic; many forms 

 live as sai)roph\'tes, many as symbionts (especially the Zooxan- 

 thellse) and still others are holozoic. Amyloid substances are usu- 

 ally present as inclusions in all types, but starch is confined to the 

 higher types. Fats and oils are occasionally found in some of the 

 colorless forms. 



Encysted stages are usually spherical, the cyst walls being made 

 of cellulose. The thickened pellicle of some forms becomes the 

 cyst wall. 



The Cryptomonadida are widely distributed in salt water while 

 fresh-water forms are relatively scarce and are never strictly plank- 

 tonic. Many types thrive in infusions where, as saprophytes, they 

 live upon dissolved proteins of disintegrating plant and animal 

 tissues; some are also holozoic. 



Pascher subdivides the Order into two sub-orders which will 

 probably be increased when the life histories of more types of marine 

 forms are better known. 



Sub-order 1. Eucryptomonadina, Pascher. 



Including the motile, flagellum-bearing types wdiich only excep- 

 tionally pass into a Palmella-stage. 



Family 1. Cryptomonadidae, Stein.— In this group are included 

 the more highl\' organized forms of the Order. The obliquely 

 truncated anterior end carries the two flagella and in the more 

 differentiated forms there is a distinct cytopharynx. Chilomonas 



