94 BIOLOGICAL LECTURES. 



an immediate direct relation between the movements of organ- 

 isms and movements characteristic of inorganic substances ; 

 a long step is taken toward that analysis of vital processes into 

 simple chemical and physical ones, which is deemed by many 

 the final goal of biological science. If these phenomena do 

 indeed establish such a relation, they challenge the attention of 

 every man interested in the fundamental phenomena of life ; 

 in any case, they invite complete and thorough investigation 

 of the claims made for them. Since it is largely from the 

 reactions of free unicellular organisms that our ideas of chemo- 

 taxis, phototaxis, and the like have been derived, it is impor- 

 tant to study carefully the reactions of these creatures and to 

 determine the laws which control them. We shall then be in 

 a position to decide whether the movements of these organisms 

 do furnish a key to the understanding of ontogenetic processes 

 or not. It is these considerations that have impelled the inves- 

 tigation whose main results I shall try to present. 



In studying the behavior of single-celled creatures we are 

 forced into relation with the much debated question of the 

 nature and importance of the activities of unicellular organ- 

 isms as compared with those of higher animals and plants. 

 Some hold that the cellular standpoint is the fruitful one for 

 general physiology ; that we must first determine the laws of 

 action for single cells, then carry these over to the cell state, 

 understanding the latter only as a combination of the former. 

 Some go so far as to maintain that the reactions of unicellular 

 organisms are of an intrinsically different character from those 

 of higher forms, being of essentially the same nature as the 

 reactions of inorganic bodies ; this is, for example, the posi- 

 tion of Le Dantec. 1 Others hold that the division of organisms 

 into cells is, physiologically at least, a secondary matter ; that 

 nothing more fundamental is to be expected from the study of 

 a unicellular organism than from that of one composed of many 

 cells. This question can be decided, of course, only by a 

 thorough study of both the classes of organisms thus con- 

 trasted, with a comparison of the results, to see if the study 

 of the simpler organisms does, as a matter of fact, clear up 



1 La mati&re vivante, Chapters I and II. 



