36 LIGHT AXD THE BEHAVIOR OF ORGANISMS 



complex. In this connection we are interested primarily 

 only in his investigations on the activities of the protozoa. 

 These were taken up in 1886, two years before Loeb's first 

 preliminary note on the reactions of animals appeared. 

 Verworn was probably the first to attempt an explanation 

 of the behavior of animals from a purely objective point of 

 view. In his papers many valuable observations are re- 

 corded on the collection of protozoa in given regions, and 

 on the orientation of these creatures when subjected to 

 stimuli of various sorts. Contrary to the idea of Loeb, he 

 concluded that the reactions to light are fundamentally 

 adaptive (1899, p. 60). His explanation of orientation is 

 of particular interest to us since it has frequently been 

 referred to in works on behavior. This he has presented 

 in his General Physiology^ (1899, P- 499) : "We will examine, 

 first, the forms that possess one fiagellum, such as many 

 Bacteria and flagellate I?ifusoria, and will select as repre- 

 sentative the delicate, green, flagellate- 

 infusorian Euglena, which, in summer, 

 ^-j".^ ^.''5 by means of its countless numbers, 



^^ changes the water of standing pools 



into a deep green. The fiagellum of 

 the Flagellata is upon the anterior pole 

 of the body and moves through the 

 water in a screw-like path. For the 

 sake of simplicity its motion may be 



considered as taking place in a single 

 Fig. 2. Scheme of the j^j^g_ j^ j^ ^^^^ ^^^^ ^^^^ -^ ^^^ij, 

 contraction of the ilagel- ^ 



lum of a flageilate-infus- lates about the Straight middle position 



'^i^t^"s:nZ [Fig- 2I by means of alternate rhythmic 



contractions toward the right (b) and 

 toward the left (bi) ; the swing out of the middle posi- 

 tion (a) into one of the two extreme positions (b or bi) 

 represents the phase of contraction; the return from one 



1 The first edition of this volume appeared in 1894 at a time when Loeb 

 was emphasizing the importance of ray direction more strongly than he 

 did later. 



