January 23, 1914] 



SCIENCE 



143 



SPECIAL ARTICLES 



SOMK PHYSIOLOGICAL OBSERVATIONS REGARDING 

 PLUMAGE PATTERNS^ 



This study was undertaken with the object 

 of carrying the analysis of the genetic factors 

 for color pattern somewhat farther than has 

 hitherto been done. In many forms of domes- 

 tic poultry the plumage of particular parts of 

 the body displays on each feather a definite 

 and regular pattern. Experimental studies 

 show that these patterns are inherited in a 

 clean-cut Mendelian manner. In the case of 

 the Barred Plymouth Rock color pattern, 

 which has been more thoroughly studied in 

 regard to its inheritance than any other single 

 plumage pattern in birds, extensive investiga- 

 tions in this laboratory and elsewhere indicate 

 that this barred pattern is represented in the 

 gametes by a single Mendelian factor or gene. 

 The manner in which this gene operates phys- 

 iologically presents a problem of great inter- 

 est, since it involves an element of morpho- 

 genetic localization. 



With a view of getting further light on this 

 matter a study has been made of the succes- 

 sive regeneration of feathers, in which special 

 attention has been paid to the comparison of 

 the pattern shown in the regenerates ard in 

 the original feather. It is the purpose here to 

 make a preliminary statement regarding this 

 work and some of the results obtained, to be 

 followed later by a detailed account. 



A word should be said in regard to one point 

 of technique, since this made possible the 

 carrying on of the investigation in a precise 

 and critical manner. The point referred to ia 

 the method used for the identification of the 

 individual feather follicle. If the feathers 

 successively produced in the same follicle are 

 to be compared, it is necessary that this par- 

 ticular follicle shall be capable of absolutely 

 sure identification at any time, whether or not 

 there is a feather present. This result was 



1 Papers from the Biological Laboratory of the 

 Maine Agricultural Experiment Station, No. 60. 

 This paper was read at the meeting of the Amer- 

 ican Society of Naturalists in Philadelphia, De- 

 cember 31, 1913. 



very satisfactorily attained by tattooing with 

 india ink a circle around each follicle chosen 

 for study. These tattoo marks are permanent 

 throughout the life of the individual and make 

 it possible to find at any time the follicle 

 which one is studying. 



A few of the more iuiportant results which 

 have been obtained from this study, which has 

 now been in progress about a year and a half, 

 may be here set forth, as follows : 



1. All feather follicles are not capable of 

 continually producing successive feathers for 

 an indefinite time. In the case of the general 

 body plumage a feather is usually not regener- 

 ated more than about three times. The pre- 

 cise number of successive regenerations varies 

 with difi'erent birds and different feathers. 

 Wing primaries seem to possess the maximum 

 regenerative capacity. After about the third 

 removal in the case of body feathers the folli- 

 cle usually remains in a perfectly quiescent 

 condition, taking no steps whatever toward the 

 regeneration of a new feather. 



2. This failure to regenerate is, however, 

 very definitely related to the natural moult of 

 the bird, and in the following way. A follicle 

 which has been absolutely inactive for a long 

 period of time (e. g., six months) preceding 

 the natural autumn moult of the bird produces 

 a new feather in connection with the moult, in 

 the same manner as does any other follicle of 

 the body. In other words the process of nat- 

 ural moulting reactivates the follicle which 

 had been brought into a quiescent state by 

 successive feather removal. 



3. The precise pattern exhibited by a par- 

 ticular feather is, in the usual course of 

 events, reproduced each time a feather is pro- 

 duced by that follicle with extreme fidelity of 

 detail. If, however, the feather is removed 

 from the follicle as soon as it is fully grown, 

 thus forcing continued regenerative activity 

 of the follicle, the pattern tends progressively 

 to be broken up, and probably will ultimately 

 be entirely lost as a definite pattern. The ex- 

 periments have not yet gone far enough to 

 enable us to speak positively on this latter 

 point. A progressive breaking up of an origi- 

 nally definite pattern is, however, very clearly 



