94 CHAS. W. HARC.ITT. 



exclusive, nor that the one class of phenomena are any less 

 related to causal antecedents than the other. But it is main- 

 tained that while in some cases these antecedents may be known, 

 and lend themselves to direction and control, on others they 

 are as yet absolutely unknown and more or less beyond pre- 

 diction or control. And furthermore, it is believed upon experi- 

 mental evidence that certain aspects of behavior may be more 

 or less variable under any given set of antecedents or conditions; 

 in other words, given stimuli do not always evoke the same response; 

 in fact, much of behavior is indeterminate in terms of existing 

 knowledge. But so far from implying a reactionary attitude 

 toward the value and importance of continued experimenta- 

 tion, the writer would hold the very opposite. It is well that 

 one pause now and then and take stock in science as well as in 

 business. That problems of behavior are complex beyond 

 earlier anticipation goes without saying. The same must be 

 admitted of every problem of biology. Only the biological 

 pessimist will find occasion to contemplate intellectual suicide 

 because he finds the dogmas of his science in process of revision! 



LITERATURE CONSULTED. 

 Bounhiol 



'oo Recherches exper. sur la rcspir. dcs annelides Etude du Spirographi-. 



Compt. Rend., T. 132, 1900. 

 Hargitt, Chas. W. 



'06 Experiments on the Behavior of Tubicolous Annelids. Jour. Exp. Zool., 



Vol. III., pp. 295-320. 

 "09 Further Observation on the Behavior of Tubicolous Annelids. Ibid., Vol. 



VIL, pp. 157-187- 



Harper, E. H. 



'09 Tropic and Shock Reactions in Perichceta and Lunihriiit^. Jr. Conip. 



Xeur. and Psych., Vol. XIX.. pp. 569-587. 

 Jennings, H. S. 



'06 Behavior of the Lower Organisms. New York. 

 Loeb, J. 



'90 \Veitere Untersuchungen uber d. Ili-lioin>pi>miis d. Tiere u. sciiu- t Ut- 

 einstimmirtig mit dem Heliotropismus drr PHanzcn. Arch. t'. d. gi--.ini. 

 Physiol., Bd. 47, p. 391. 



'oo Comp. Physiol. Brain and Comp. Psych. New York. 

 Mast, S. O. 



"ii Light and the Behavior of Organisms. New York. 

 Nagel, W. A. 



'96 l)cr Lichtsin augenloser Tiere, cine biologische Studie. Jena. 

 Radl, Em. 



'03 Untersuchungen ubcr den Photntropismii^ drr lirir. 



