186 BIOLOGY OF THE PROTOZOA 



visible within the tentacle. In some cases it is said that the endo- 

 plasm of the captor flows through the tentacle and into the body sub- 

 stance of the prey where the latter is digested (Maupas, 1883). The 

 body of the victim graduall\' collapses luitil nothing remains but the 

 denser walls and the insoluble parts. 



Many of the Protozoa, while parasitic in the caA'ities and cells of 

 different animals, retain the holozoic method of food-getting, feeding 

 upon parts of the protoplasm of the host or upon other living organ- 

 isms such as bacteria of the digestive tract, or solid detritus of 

 one kind or another. Thus Endainoeha coll lives on intestinal 

 bacteria, while Endamoeha dysentericB, Craigia hominis, etc., engulf, 

 with other food substances, red blood corpuscles and digest them. 

 According to Haughwout (1919), the flagellate Peniatrichoinonas 

 sp. likewise ingests red blood cor])Uscles. In the majority of pro- 

 tozoan parasites, however, the organisms do not digest the food 

 necessary for the growth of their own protoplasm. They practically 

 li^'e in a huge gastric vacuole and are surrounrled by food already 

 digested or partly digested, which is absorbed by osmosis through 

 their body walls. Doflein thinks that such food substances, if not 

 appropriate for the up-building of protoplasm of the parasite, may 

 be made suitable by the secretion from the parasite of special diges- 

 tive substances and is ready for absorption after the action of such 

 secretions. He further suggests that the cytolytic action upon cells 

 and tissues of the host may be due to such secretions (for example 

 Endamceha dysentcrioe) and that other toxins of pathogenic Protozoa, 

 probably enzymatic in their activity, may be similar digestive secre- 

 tions from the parasites (see p. 190). 



Secretions and Digestive Fin ids. — Vroductn of metabolic activity 

 in the form of secretions and precipitations play most important roles 

 in structure and activities of all kinds of Protozoa. Skeletons, shells 

 and tests, gelatinous mantles, stalks, cyst and spore membranes, 

 and the like are all evidences of the secretory activity of the proto- 

 zoan protoplasm (see Chapter III). There is evidence that these 

 activities, like secretory activity of the gland cells in Metazoa, are 

 dependent upon the general function of irritability and that specific 

 secretory response follows a specific stimulus. Thus Breslau (1921) 

 finds that gelatinous mantles or tubes about CoJpidiuni coljjoda may 

 be called forth at will by the use of certain chemicals (iodine, fatty 

 acids). If fatty acids are used, the individuals, as in artificial 

 parthenogenesis, must be replaced iji a suitable medium before the 

 membranes are formed. Enriques (1919) gives evidence to show 

 that the secretion of stalk material in Anthophysa vegetans depends 

 uj)on the quantity of food available. Stimulation, through the 

 agency of foreign proteins, is without much doubt responsible for 

 the secretion of digestive fluids and ferments in holozoic nutrition, 

 and considerable advance has been made in our knowledge of intra- 



