CHAPTER IV 



PHYSIOLOGY: "RED WATER," NUTRITION, REACTIONS TO 



STIMULI, LUMINESCENCE 



In the Protozoa we find all life processes reduced to their simplest expres- 

 sion. This makes for simplicity of function, but since these functions are all 

 carried on ^Yithin the compass of a single microscopic cell it often conduces 

 also to complexity of organization. As not infrequently happens, a single group 

 of organisms may present a wide I'ange of structural differentiations, with con- 

 sequent modifications of physiological activities. 



This is particularly true of the Flagellata, which present the elementary 

 ch.n/acteristics of both plant and animal organization. The dividing line be- 

 tween these two types of organization and the resiilting physiological activities 

 which mark the plant and animal kingdoms cannot be dra^vn with certainty 

 between orders, families, genera or even species among certain Protozoa, since 

 in some groups even related species may respectively exhibit the two types of 

 organization. Such a group is the Dinoflagellata. In the members of this 

 group we find forms of the simplest tyjje of organization, as well as some which 

 exhibit the highest degree of specialization, in some features, to be found within 

 the Protozoa, and we find also tjq^es of nutrition ranging from the typically 

 plant method through saprophytic to the typically animal mode of food-getting. 

 This condition makes these organisms of peculiar interest to the biologist be- 

 cause of this intimate interrelation of such diverse functions. 



The physiological activities of this group have, however, received but little 

 attention. A few scattered references to the subject may be found in the liter- 

 ature, but the data given on such constituent parts of the body as starch grains, 

 am3doid bodies, etc., have usually not been based on definite experimentation 

 and therefore are inconclusive. No work has thus far been done along this line 

 by the present authors, hence this subject can only be touched upon lightly, 

 with tentative conclusions which must await definite experimentation for 

 confinnation. 



The dinoflagellates probably rank next to the diatoms in their abundance 

 in the sea and in their importance as a food supply for the smaller plankton 

 life which feeds upon the great oceanic meadows. Examinations of the stomach 

 contents of sardines and other small fish reveal the fact that a very large per- 

 centage of the food used by these animals consists at times of dinoflagellates. 

 In many parts of the ocean and at some seasons of the year these flagellates 

 far outrank the diatoms in aljundance, and become the dominant forms for 

 longer or shorter periods of time. At such times they may become a menace 

 to the slow-moving or })ottom-living animals. The unusual amount of oil and 



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