THE PROBLEM 6 



nature of climatic factors which undergo rhythmical time-changes, 

 the elementary processes of the struggle for life take place there amid 

 a totality of most diverse living beings. This totality presents a 

 whole, and the separate elementary processes taking place in it are 

 still insufficient to explain all its properties. It is also probable that 

 changes of the totality as a whole put an impress on those processes 

 of the struggle for existence which are going on within it. 



Nobody contests the complexity of the phenomena taking place in 

 the conditions of nature, and we will not enter here into a discussion 

 of this fact. Let us rather point out all the importance of studying 

 the elementary processes of the struggle for life. At present our 

 position is like that of biophysicists in the second half of last century. 

 First of all it had been necessary to show that separate elementary 

 phenomena of vision, hearing, etc., can be fruitfully studied by physi- 

 cal and chemical methods, and thereupon only did the question arise 

 of studying the organism as a system constituting a whole. 



(5) Certain authors at the close of last century occupied themselves 

 with a purely logical and theoretical discussion of the struggle for 

 existence. They proposed different schemata for classifying these 

 phenomena, and we will now examine one of them in order to give 

 just a general idea of those elementary processes of the struggle for 

 life with which we will have to deal further on. To the first large 

 group of these processes belongs the struggle going on between groups 

 of organisms differing in structure and mode of life. In its turn this 

 struggle can be divided into a direct and an indirect one. The 

 struggle for existence is direct when the preservation of life of one 

 species is connected with the destruction of another, for instance that 

 of the fox and the hare, of the ichneumon fly and its host larva, of 

 the tuberculosis bacillus and man. In the chapter devoted to the 

 experimental analysis of the predator-prey relations we will turn our 

 attention to this form of the struggle. In plants, as Plate ('13) points 

 out, the direct form of the struggle for existence is found only in the 

 case of one plant being a parasite of the other. Among plants it is the 

 indirect competition, or the struggle for the means of livelihood that 

 predominates; this has also a wide extension among animals. It 

 takes place in the case when two forms inhabit the same place, need 

 the same food, require the same light. We will later give a great deal 

 of attention to the experimental study of indirect competition. To 

 the second group of phenomena of the struggle for life belongs the 



