224 G. U. PARKER 



and the like; the other brings into prominence the unified action 

 of these animals and interprets their behavior from the stand- 

 point of the whole organism. It is by no means clear that these 

 differences of opinion are really as pronounced as they some- 

 times appear on paper, but it is perfectly evident that the two 

 general views represent real differences on a subject about which 

 the truth can not at present be easily stated. 



More or less of this difference is doubtless due to the various 

 methods of attack which different investigators have used in 

 this field of work. Since the external stimuli are more easily 

 measm-ed and otherwise controlled than the internal states, these 

 were naturally first studied with the result that the work of 

 Loeb, Nagel, and others led to a general conception of an actin- 

 ian as a delicately adjusted mechanism whose activities were 

 made up of a combination of simple responses to immediate 

 stimulation. This view has been criticised by Jennings ('05, p. 

 448) as giving an unnaturally sharp, clear-cut and simple pic- 

 ture of actinian behavior. Jennings, moreover, has drawn atten- 

 tion to the physiological state of the animal including the effects 

 of previous stimulation, of its metabolism and so forth, in fact 

 of its general past history, as an internal element of no small 

 importance in interpreting its reactions. Jennings' view has 

 much to commend it, but, if assumed exclusively, it too has its 

 limitations. As von Uexkiill ('09, p. 74) and Baglioni ('13, p. 

 48) have recently pointed out, it too often tempts the worker to 

 be satisfied with the statement of inferred internal states as 

 explanations of conditions which upon careful scrutinizing prove 

 to be dependent upon quite different factors, and the consequent 

 vagueness and uncertainty with which it often surrounds the 

 subject obscures the real questions for investigation. Keeping 

 in mind these two tendencies, what can be said about the psy- 

 chology of actinians? First of all it seems fairly certain that 

 their behavior is chiefly determined by their immediate environ- 

 ment. They are expanded or retracted, feeding or quiescent, 

 creeping or still in consequence of immediate stimulation rather 

 than as a result of internal states due to past activities. They 

 exhibit rhythmic responses only to immediate rhythmic stimuli, 



