GENERAL PHYSIOLOGY 167 



organization; some of these are evident in indi vicinal life between 

 division periods ; others are evident only in a long series of individuals 

 constituting a life cycle. These will be more fully treated in 

 Chapters X and XI. 



Other changes in organization may be brought about by environ- 

 mental conditions; or they may be brought about by changes in 

 one or more of the substances constituting the protoplasm of the 

 species, as when amphimixis introduces a new^ combination of chro- 

 matin into the organization. These are undoubted factors in the 

 phenomena of adaptation and probably play a part in the origination 

 of new species and types. 



In presenting the physiological aspects of the Protozoa in this 

 and in the later chapters, I shall endeavor to follow out the 

 train of thought outlined above. The more obvious functional 

 activities of the individual will be considered first, and will be 

 followed by a discussion of vitality or the sum total of activities in 

 the life cycle and the changes in organization which accompany the 

 changes in vitality. Sex phenomena, including gamete formation 

 and maturation, will be treated as evidences of cyclical differentia- 

 tion in the organization, while fertilization phenomena will be con- 

 sidered from the standpoints of their bearing on reorganization and 

 vitality and on the origin of specific variations. 



FUNCTIONAL ACTIVITIES OF THE INDIVIDUAL. 



The sum total of the various physiological processes of the 

 individual may be subdivided for the Protozoa, as they are for the 

 Metazoa, into aggregates of special activities which we call the 

 fundamental vital functions, and distinguish as nutrition, excretion, 

 irritability and reproduction. In Metazoa these are performed by 

 specialized cells, grouped into tissues, organs and organ systems, 

 the complexity varying with the specialization of the organism. 

 In Protozoa they are all performed by the single cell and all are more 

 or less involved in the activities of the diverse substances and struc- 

 tures which compose it. All work together in a harmonious cycle 

 of matter and energy. 



The scientific beginnings of the modern mechanistic conception 

 of vital activities is traced to Lavoisier and his comparison of animal 

 heat with physical heat due to combustion through oxidation. The 

 utilization of chemical energy or energy of combination liberated 

 by oxidation, is possibly the keynote to the multiple vital harmonies 

 of animal life (see Verworn, 1907). Oxygen necessary for such 

 physiological combustion is obtained by all protozoa without the 

 aid of specialized respiratory organs. It is readily absorbed through 

 permeable membranes from the surrounding water, or obtained 

 by reduction from oxygen-holding substances, as in anaerobic forms. 



