RELATING TO SECONDARY SEXUAL CHARACTERS. 85 



the light for a week or two and meal-worms were added to the diet. 

 This invariably resulted in a full resumption of song, 



"I foxind that a sudden alteration in temperature — either lower or higher — 

 wrought a radical change in the physical metabolism of the birds. They 

 would stop feeding almost altogether, and one tanager lost weight rapidly. 

 A few feathers on the neck fell out, and in the course of some two weeks tMs 

 bird moulted almost every feather and came strongly into his normal winter 

 plumage of ohve green. The metaboUsm set up by the change in temperature, 

 in its intent and rapidity, seems comparable only to the growth of a deer's 

 antlers. 



"Early in the following spring individual tanagers and boboUnks were grad- 

 ually brought under normal conditions and activities, with quick result; just 

 as the wild birds in their winter haunts in South America were at that time 

 shedding their winter garb and assuming the most brilUant hues of summer, so 

 the birds under my observation also moulted into the colors appropriate to the 

 season. The old scarlet and black feathers fell from the tanagers and were 

 replaced by others of the same color; from buff, cream, and black, the bobo- 

 Unks moulted into buff, cream, and black ! There was no exception ; the moult 

 was from nuptial to nuptial, not from nuptial to winter plumage. The dull 

 colors of the winter season had been skipped." 



How are these results to be interpreted? Obviously the environ- 

 ment prevented the autumn molting; hence the birds necessarily 

 retained their nuptial plumage. But is this the whole story? Did they 

 not also remain sexually active with their testes producing sperm as in 

 the mating season? In other words, if feathers had been plucked from 

 them, would not the new feathers have been like those already present? 

 Despite the author's statement that not a single feather was molted, 

 is it not likely that occasionally a feather must have been accidentally 

 lost. If even one had been lost and an eclipse feather had replaced it, 

 the effect would not have escaped so keen an observer as Dr. Beebe. 

 It seems to me not unlikely that an occasional feather may have been 

 lost and replaced by a nuptial one. If so, then the results are most 

 probably interpreted as due to the birds having remained sexually 

 active. This condition suppressed the autumn molt, and at the same 

 time would cause any single feather lost to be like those still present. 

 In support of such a conclusion I can appeal to Beebe's statement that 

 after a week in the light a full resumption of the song took place. It 

 is unlikely that sexual maturity would be attained in so short a time 

 unless the birds were already in the condition of sexual vigor. Perhaps 

 one can appeal also to Beebe's other statement, viz, that after a sudden 

 change in temperature, followed by a changed metabolism and loss of 

 weight, the birds molted and assumed the eclipse (winter) plumage. 

 Here I should interpret the facts cited possibly to mean that the males 

 lost their sexual activity and in consequence developed the eclipse 

 plimiage. 



Until further information is obtained judgment must be suspended. 

 If, as Beebe's statements strongly suggest, the external conditions, 



