198 BIOLOGY OF THE PROTOZOA 



probably a modified form of chlorophyll, the transition being brought 

 about by scarcity of nitrogen or phosphorus. "Red snow" or 

 "bloody pools" owe their origin to masses of these flagellates colored 

 by karotin, which, according to the observations of Reichenow 

 (1909) disappear from alpine red snows or pools in summer when, 

 through decaying vegetation, the waters are richer in organic 

 compounds. 



Little is known accurately of the method by which organic food- 

 stuft's are manufactured by chlorophyll and practically nothing is 

 known about the process in Protozoa. Presumably the activities 

 here are the same as in the higher plants, food manufacture being a 

 result of photosynthesis. The spectrum of chlorophyll shows 

 absorption particularly of the short wave rays of light— notably 

 blue and green regions of the white light spectrum, and in some way 

 not yet imderstood, the kinetic energy of sunlight, transformed 

 into potential energy of chlort)j)hyll, is utilized in the synthesis of 

 organic compounds. Carbon, hydrogen and oxygen are essential 

 for carbohydrate synthesis, and nitrogen must be added to form 

 protein. Such combinations require energy and undoubtedly the 

 energy obtained from sunlight supplies this need. While CO2 

 and HoO are essential for plant activit\', little is known of the exact 

 manner in which they are essential. Also, while CeHioOa or starch 

 may be derived on paper by combining 6 molecules of the one and 

 5 of the other, the exact process is unknown, and the chances are 

 that it is not so simple as appears by the equation. The sensitive- 

 ness of chlorophyll, or its extreme lability in light and darkness, its 

 first appearance only in the light, are factors indicating an intimate 

 physiological dependence upon the radiant energy of the sun. It 

 is not altogether satisfactory to assume that chlorophyll uses this 

 energy as one would use a tool, to separate the elements of COo 

 and HoO, and to unite them again into CHoO or formaldehyde, and 

 then to use it again in the condensation of CHoO into CeHioOe or 

 sugar; or to use it directly for condensing H0CO3 into CeHiaOe and 

 O2. The instability of chlorophyll; its disappearance under unfav- 

 orable and reappearance under favorable conditions, leave little 

 basis for the assumption that it remains unchanged throughout 

 the reactions which it is responsible for bringing about. The 

 experiments of Jorgensen and Kidd (1916) whereby extracted 

 chlorophyll in sunlight ])roduced no formaldehyde in an atmosphere 

 of pure CO2, but did ])r()(luce it in an atmosphere of pure oxygen, 

 indicate that formaldehyde formation and production of carbo- 

 hydrates in plants may be a result of oxidation and not of synthesis 

 in atmospheric air. 



If Wilstiitter's formula for chlorophyll is approximately correct 

 we have a protein molcule thus— (MgN4C32H3oO) (COOCHs) 

 (COOC20H39) in which the chromogen radical (MgN4C32ll3oO) may 



