270 BIOLOGY OF THE PROTOZOA 



the two valves and the median suture, and they are so treated in 

 the following classifieation. 



The marine form O.vyrrhis uiarhia, which as Senn was the first 

 to demonstrate, should be placed with the Dinoflagellida, has a 

 rather indefinite groove and two free flagella (Fig. 43, p. 88). 

 The flagellated swarmers of Noctihwa mUiaris have a similar groove 

 while one of the flagella disappears and a well-marked tentacle 

 characterizes the adult. 



In addition to the transverse groove the majority of the Dino- 

 flagellida have a more or less clearly marked longitudinal furrow or 

 sulcus which crosses the transverse furrow at the region of the 

 flagella insertion. In many cases this does not extend beyond the 

 transverse groove and is confined to the posterior half of the cell; 

 in other cases however, it extends nearly from pole to pole. 



The flagella are two in number, one the transverse flagellum 

 which may be band-form, vibrates in the groove or, in Adinina, in 

 a circle free from the anterior end of the organism. The other 

 flagellum is more thread-like and vibrates freely in the water. The 

 combined activity of the two gives the characteristic whirling move- 

 ment of the dinoflagellate t^^e. 



A retractile tentacle is present in Erylhropsis while pseudopodia 

 have been described by Zacharias in the case of (iymnodinium 

 zachariasi, Lemm. Pascher has described an amoeboid organism 

 which he calls Dinamoeba (see Leidy) wdiich, like Noctihwa, repro- 

 duces by the formation of dinoflagellate-like swarmers (dinospores). 



Chromatophores of green, yellow or brown color and from two, 

 large, to many small, discoidal structures are generally present, but 

 are absent here and there in all groups and in all species of the bathy- 

 metrical group. Nutrition is autotrophic or heterotrophic, the 

 chl()ro])hyll-bearing forms being autotrophic for the most part 

 although the ingestion of solid food substances by such types has 

 been repeatedly observed. Some forms are parasitic, (iymnodinium 

 puhisculus according to Pouchet (1886) is an ectoparasite on Salpa, 

 Appendicularia, Siphonophora and other marine pelagic animals, 

 while (iymnodinium parasiticnm, according to Dogiel, is an endo- 

 parasite in copepod eggs. One entire group furthermore— the Blas- 

 todinidee— are parasitic (see Chatton, 1920). 



Stigmata, also, while not universal, are widely distributed and 

 in some cases are accompanied by a crystalline am\'loid structure 

 which appears to fiuiction as a lens (Faure-Fremiet ; Schiitt). 



Vacuoles of a somewhat different type from the usual contractile 

 vacuoles are always present. They are filled with a clear fluid and 

 appear to have definite walls, opening to the outside in the region 

 of the flagella fissure. Two types of these \'acuoles are usually 

 present, one, called the collecting i)usule b\' Schiitt may be sur- 

 rounded by a ring of small casual vacuoles (Kofoid) and resemble 



