194 BIOLOGY OF THE PROTOZOA 



The biochemistry of the process is practically unknown, and few 

 experiments on strictly saprozoic forms have been made. Khawkine 

 (1885, 1886) was apparently the first to demonstrate that chloro- 

 phyll-bearing flagellates (Euglena) can live more or less perfectly 

 as saprozoic organisms. This was further elaborated by Zumstein 

 (1600), who showed that Evglena gracilis can live in a colorless and 

 in a chlorophyll-bearing condition. It was long since suggested 

 hypotheticall.^', and later verified experimentally, that organic 

 matters are taken into green flagellates from the surrounding 

 medium. Zumstein endeavored to find out whether such organic 

 matters consist of carbon compounds, or nitrogen and ammonia 

 compounds, and found that in a bacteria-free medium, peptone 

 with the addition of some carbohydrate gave the best results. 

 Ternetz (1912), confirming Zumstein's main results, foimd that the 

 best sources of nitrogen were asparagin, glycocoll, and alanin, while 

 amtnonia compounds were generally detrimental. 



From such experiments, it appears probable that saprozoic forms 

 of Protozoa get their main nourishment from amino-acids derived 

 from disintegration of animal and ])lant matter through the agency 

 of bacteria, and from carbohydrates in solution. The necessary 

 mineral matters are obtained from the surrounding alkaline medium. 



In this connection, it is important to consider the possible inter- 

 action of excretion products of dift'erent Protozoa upon themselves 

 and upon each other, as well as the effects of products of bacterial 

 action. It has long been known that isolation cultures are fre- 

 quently threatened by the growth of detriniental bacteria. On 

 a priori grounds it is not improbable that excretion products of 

 Protozoa themselves may have such an effect. Woodruff' (1912, 

 1913) has studied this problem in connection with Paramecium 

 anrclia and the hypotrichous ciliates, Stylonychia pusiadata and 

 Pkurotricha lanceolata, and found that Paramecium when placed 

 in filtered medium, which had contained enormous numbers of 

 Paramecium in pure culture, were manifestly weakened in ^'italit^^ 

 Similarly the hypotrichs when placed in filtered medium which had 

 swarmed with hypotrichs, showed a weakened vitality. When, 

 however, Paramecium was placed in filtered hypotrich culture 

 medium, the result was an increased A'itality. Woodruff' concluded 

 that excretion products from Paramecium are detrimental to 

 Parameci^im, and hypotrich products to hypotrichs, while the 

 latter products have a somewhat stimulating effect on Paramecium. 

 This may be, as Woodruff' suggests, of some importance in deter- 

 mining the sequence of protozoon forms in a limited environment 

 such as hay infusion. 



Parasitic nutrition is not a specific form of nutrition and refers 

 to the effect upon a host, rather than to any physiological activity 

 of the parasite itself. Nutrition of parasites, indeed, may follow 



