74 PROTOPLASM OF PROTOZOA 



unless shell materials are present in the cultures in which the organisms 

 are grown; shell materials are collected just previous to division, but 

 before nuclear changes have begun. Verworn (1888) has found that 

 only after mechanical irritation of the pseudopodia of Dijjlugia do they 

 become sticky enough for glass particles to adhere to them, to be later 

 drawn into the shell. Foreign particles may adhere to the surface of a 

 moving amoeba and be carried forward by the outer layer, sometimes 

 making many complete revolutions. Parsons (1926) has observed that 

 carmine granules adhere to and move over the surface of an amoeba 

 floating in distilled water, although there has been a definite loss of ca- 

 pacity for adherence to substratum. Then, too, the outer layer of Fo- 

 raminifera and Heliozoa is quite fluid, serving to capture food organisms 

 which adhere to the surface. Certain of these organisms (i.e., Acti- 

 nophrys) have been reported to form temporary colonies and to capture 

 large objects of prey; such temporary colonies may be induced by me- 

 chanical means (Looper, 1928). However, it has been shown by Daw- 

 son and Belkin (1929) and Marsland (1933) that the adhesion between 

 A. dubia and an oil surface is distinct from the process of ingestion, 

 since a cap of oil may adhere to and spread over the tip of a pseudopod 

 without ingestion taking place. The relation of adhesion to phagocytosis 

 has been extensively studied in the amebocytes of the invertebrate Meta- 

 zoa (see Faure-Fremiet, 1930; Loeb, 1927, 1928). 



A remarkable example of the stickiness of protoplasm is shown by 

 the Choanoflagellata, in which the flagellum is surrounded by a proto- 

 plasmic collar; food particles, brought to the collar by the movements 

 of the flagellum, adhere and are carried to the point of ingestion by the 

 flowing protoplasm of the collar. Some flagellates [Heteromita and 

 Oikoinonas) have pseudopodia which are primarily adhesive in func- 

 tion. While flagella are primarily organs of locomotion, they frequently 

 are used as organs of attachment. This is commonly observed in Costia, 

 Chilomonas, Heteromita, Pleuromonas, Anisonema, and Vetalomonas. 

 The nature of this adhesion is not known. 



Certain of the developmental forms of trypanosomes become at- 

 tached by their flagella to the walls of the organ of the invertebrate host 

 in which they are found. Lwoff (1934) has mentioned that Strigomonas 

 oncopelti and 5". jasciculata may swim free in cultures or may fasten to 

 the glass side of the culture dish; they release upon a few seconds heating 



