FROG'S HAIR 



African Batrachian Possesses Hair-like Appendages Whose Origin Is Shrouded 

 in Mystery— Probably Secondary Sexual Character 



FROG'S HAIR" has lon^ been 

 an infijrcdient of popular meta- 

 phor, and considered as myth- 

 ical as the equally famous 

 "hen's teeth." When, therefore, G. A. 

 Boulenger described in 1900 two frogs 

 from the German Congo which had a 

 partial covering of what looked very 

 much like hair, his description did not 

 fail to awaken a deal of interest, 

 among those who came across it. 



Were the mammals to lose one of 

 their distinguishing characteristics, 

 through its extension to the frogs? 

 Boulenger admitted that he did not 

 know much about it, but said that these 

 "villose dermal i)apillae" were not a 

 nuptial attribute of the males, but were 

 rather more strongly developed in the 

 female than the male. He suspected 

 them of being a seasonal ap]:)endage. 



In 1902 he ]jublished another short 

 paper on the subject describing seven 

 more specimens of the same species 

 (Astylostermis robustus Blgr.). In this 

 case the females showed no trace of the 

 appendages, while in the two males 

 they were fully developed. The s])cci- 

 mens were evidently obtained during 

 the breeding season. 



Meantime Dr. H. Gadow had made a 

 microscopical examination of the hair- 

 like structures, and reported that he 

 was unable to find any nerves in them, 

 although he made out some insignificant 

 blood vessels and lymph spaces. He 

 concluded that these appendages could 

 not be considered a sensory a])])aratus, 

 and agreed with Boulenger that their 

 function was a mystery. 



There the case remained until Willy 

 Kiikenthal, working in the Museum of 

 Comparative Zoology at Harvard Col- 

 lege, reviewed it' by the study of eleven 

 specimens from Kribe, Kamerun. He 

 established that the hair-like appcnciages 

 were ]:)resent only in the males, and 



altogether wanting in the females. 

 This confirms Boulenger's second report ; 

 evidently his first one was an error. 



It was further found "that these 

 appendages do not attain the same 

 degree of development in all male 

 individuals, and that even in full grown 

 males there are very conspicuous differ- 

 ences in this regard." 



He believes, although data are few, 

 that the hair-like covering is most 

 highly developed during the breeding 

 season, and that it is to be considered a 

 secondary sexual characteristic. 



"The fact that a younger (smaller) 

 male, contained in the same jar with 

 the two adult males possessing fully 

 developed appendages — and therefore 

 apparently ca])turcd at the same time 

 with these — showed this hair\' coat in 

 its beginnings, points to the conclusion 

 that the appendages are fully developed 

 only on adult animals and probably, as 

 I have already .suggested, at the time of 

 mating. 



"Now arises the question, from what 

 do these organs originate? The reply 

 requires a careful investigation of the 

 female. It is quite surprising, that 

 none of the former investigators has 

 observed the fact, that the females 

 have, on exactly the same parts of the 

 body that on the males bear these 

 appendages, small but quite distinct 

 tubercles, which have the same diameter 

 as the bases of the ai)i)endages in the 

 males. Their distribution over exactly 

 the same areas of the .surface shows 

 clearly that they are homologous willi 

 the ajjpendages of the male. 



"Moreover, if we carefully study the 

 surface of the skin, we find that both 

 males and females show similar tubercles 

 scattered over the whole back, and that 

 they are more closely crowded in the 

 region of the angle of the jaws. In 

 some areas of the surface of the males 



'Bull. Mus.Comp.Zool. at Harvard CoUc-j^n-, Vol. LIII, .\:). 0, pp. M\-M(^, 1 fijjs., .S plates. 

 362 



