Mat 10, 1907] 



SCIENCE 



725 



animal ceases to respond to this stimulus 

 but is still normally sensitive in that part 

 of its body to heat or to mechanical stim- 

 ulation. In a similar way after exhaustion 

 to mechanical stimulation or to heat stim- 

 ulation, the particular part of the body 

 experimented upon is still sensitive to the 

 other classes of stimuli. Exhaustion to 

 light stimulation has no effect upon the 

 sensitiveness to the other classes of stimuli. 

 These observations lead to the conclusion 

 that light, heat, mechanical and chemical 

 stimuli are received by physiologically sep- 

 arate mechanisms and that these mechan- 

 isms are located in the skin except in the 

 case of light, whose receptive organs are 

 the pigment cups in the central nervous 

 organ. 



Analysis of the Cyclical Instincts of Birds: 



Francis H. Herrick, "Western Eeserve 



University. 



The behavior of wild birds is primarily 

 determined by a number of commanding 

 instincts of ancient origin. These cardi- 

 nal instincts are of two kinds, namely: (1) 

 continuoxis instincts, which are needed for 

 the preservation of the individual, such as 

 preying, fear, concealment and flight, and 

 (2) cyclical iTistincts, which are necessary 

 for the maintenance of the race. By 

 cyclical instincts we mean those discon- 

 tinuous, recurrent impulses which attend 

 the reproductive cycle, and which may be 

 described as parental instincts. 



The cyclical or parental instincts as a 

 rule recur with almost clock-like precision, 

 in spring or summer, with repetitions 

 within the breeding season in certain 

 species. They are modified by the con- 

 tinuous instincts, such as fear, and the in- 

 stinctive behavior as a whole is liable to 

 modification at every point by intelligence. 

 Neglecting such changes for the present, 

 we will briefly analyze the cyclical in- 



stincts, reserving details and tabular state- 

 ments for a fuller presentation. 



The reproductive cycle is made up of a 

 series of terms, representing discrete acts 

 or chains of actions which follow in a defi- 

 nite succession. Eight or more terms may 

 be recognized, many of which, such as 

 brooding and feeding the young, are recur- 

 rent within the series. The cycle may be 

 graphically represented by a number of 

 tangent circles, each one of which stands 

 for a distinct sphere of influence, or subor- 

 dinate series of related impulses, named 

 and numbered as follows: (1) Spring mi- 

 gration; (2) courtship and mating (often 

 attended by song) ; (3) selection of nesting 

 site and building nest (often accompanied 

 by the fighting instinct); (4) egg-laying; 

 (5) incubation— including care of eggs, 

 such as shielding, rolling, cleaning and 

 covering (fear often completely blocked by 

 brooding instinct) ; (6) care of young in 

 nest, subject to the following analysis: 

 (a) feeding young, including capture and 

 treatment of prey, return to nest (pause), 

 call-stimulus, testing reflex response of 

 throat, watching for reflex response 

 (pause); (&) inspection of young and 

 nest; (c) cleaning young and nest; removal 

 and disposition of excreta; (d) incidental 

 care of young and incidental behavior in 

 this and other terms of cycle, such as brood- 

 ing, shielding or spreading over young 

 whether sitting or erect, bristling and 

 puffing, preening, gaping, stretching and 

 yawning, guarding and fighting; (7) care 

 and incidental education of young when 

 out of the nest; guarding, feeding, play, 

 and other instinctive acts; (8) fall migra- 

 tion. Beginning at 2, 3 or 4, according to 

 circumstances, the cycle may be repeated 

 once or oftener within the season. 



The coordinated instinctive responses of 

 the young begin in the sixth term, and 

 are mainly as follows: (6) Initial responses 

 at moment of hatching or shortly after, 



