126 



THE PROTOZOA 



Where the flagella are in separate groups, there is a mouth at the 

 base of each group. The collar of the Choanoflagellida is especially 

 adapted for the collection and direction of the food particles into the 

 interior. 



Perty ('52), Kent ('81), Stein ('67), Entz ('88), and others have 

 described a number of types which they claim have both kinds of 

 nutrition, and are intermediate between the holozoic and holophytic 

 forms ; but Biitschli, although he admits that food-taking may be 

 either holozoic or holophytic in one form at least {Chromulina flavi- 

 cans), which lives equally well when one or the other mode of 



nutrition is prevented, is inclined to 

 doubt the wide distribution of this 

 double function. Meyer ('97) main- 

 tains that in one form {Ochromonas 

 granulosa) the organism may be either 

 holozoic, saprophytic, or holophytic in 

 nutrition. In many of the holophytic 

 forms, there is a distinct gullet, which 

 Perty and Kent regarded as a food- 

 taking organ and, therefore, evidence 

 of holozoic nutrition. Biitschli, how- 

 ever, maintained that it is a part of the 

 excretory system and connected with 

 the contractile vacuole {Euglcjta, Cryp- 

 tomonas, etc.). 



A close connection between holozoic 

 and holophytic forms is found, not only 

 in Flagellidia, but in Dinoflagellidia as 

 well. Possessing chromatophores and a coating of modified cellulose, 

 these organisms were for a long time regarded as plants, but some 

 forms among them are known to move about like animals and to ingulf 

 solid food. Such forms may be either naked, as in Gymnodiuium (Fig. 

 64, A) and Polykrikos, where food-taking has been actually seen by 

 a number of observers (Schmarda, Stein, Bergh, Schilling, Dangeard), 

 or shell-bearing, as in Glcnodinium edax (Schilling). It is probable 

 that they are much more closely related to the animal Flagellidia than 

 to the Diatomacece (as Warming maintains), or other plants, although 

 no hard and fast line can be drawn about any of these groups. 



The food of the holozoic flagellates consists of bacteria and minute 

 bits of disintegrated proteid matter. These in the Rhizomastigidas, 

 as in the Rhizopoda, are surrounded by pseudopodia, and are subse- 

 quently drawn into the body. In other Mastigophora, the flagellum 

 is the chief factor in alimentation, and by its vibrations a current is 

 created toward the base, where the mouth or its equivalent is 



Fig. 71. Megastoma entericum Grassi 

 Ventral and side views. [GRASSI.] 



