4 FREDERICK S. BREED 



accuracy of pecking. Katz and Revesz ' support Hess ^ in the 

 view that the hungry chick does not peck at food which it does 

 not see. The former assert, for example, that a chicken in the 

 dark-room, even if placed directly in the food, will not peck 

 at it. The point happens to be vital to their method in some 

 important work. 



It has seemed best to report the essential conclusions of the 

 writers mentioned, so far as possible, in their own words. It 

 may not be amiss, however, to note two general impressions 

 one gets from these studies of the pecking instinct: (i) that 

 the reaction has a high degree of congenital accuracy, and (2) 

 that it has less of this than was formerly supposed. 



III. General Apparatus 



The room used for these experiments had a western exposure. 

 It was equipped with an incubator ' and a brooder * so that 

 chicks for the experiments might be hatched at any time during 

 the year in the laboratory. Such an arrangement also provided 

 a good opportunity for complete knowledge of the history of 

 the animals. For the sake of safety, economy, and convenience, 

 both brooder and incubator were heated with gas. In addition 

 to the regular thermostat on the incubator, a gas regulator * 

 was attached to insure a more constant temperature. No trouble 

 was experienced at any time in securing eggs of the special 

 kind desired. The incubator and brooder were easily operated 

 after a careful study of the directions that came with the 

 machines. The percentage of fertile eggs hatched during the 

 first year was 65.6. At times two settings were run simulta- 

 neously in the same incubator. 



'Katz, D. und R^v^sz, G.: Experimentell-psychologische Untersiichungen mit 

 Hvihnern. Zeitschrift f. Psych, u. Physiol, d. Sinnesorgane , 1909, Bd. 50, S. 93. 



^ Hess, C: Ueber Dunkeladaptation und Sehpurpur bei Htihnern und Tauben. 

 Archiv f. Augenheilkunde, 1907, Bd. 57, S. 298-316. 



— : Untersuchungen iiber Lichtsinn und Farbensinn der Tagvogel. 



Ibid., 1907, Bd. 57, S. 317-327. 



: Untersuchungen iiber die Ausdehnung des pupillomotorisch 



wirksamen Bezirkes der Netzhaut und iiber die pupillomotorischen Aufnahme- 

 organe. Ibid., 1908, Bd. 58, S. 182. 



: Untersuchungen iiber das Sehen und uber die Pupillenreaktion 



von Tag-und von Nachtvogeln. Ibid., 1908, Bd. 59, S. 143-167. 



^ Junior No. 2, sold by the Prairie State Incubator Co., Homer City, Pa. 



■* Indoor Brooder, No. 5, sold by the same firm. 



' Single Float Standard Automatic Gas Regulator, secured from the Gas Con- 

 sumers' Association, 18 Boylston St., Boston, Mass. 



