ACQUIRED CHARACTERS 315 



periodically pulling these feathers throughout the life-time of 

 individuals during successive generations. And Mr. J. T. 

 Cunningham has endeavoured to show (^Sexual Dimorphism in 

 the Anim.al Kingdom^ that all the varied ornaments of birds, 

 whether in the shape of feathers or of horny or fleshy excres- 

 cences, have been gradually "acquired" as a consequence of 

 the stimulus of use during successive generations. But no 

 evidence that lends the slightest support to such an hypothesis 

 has yet been produced. 



But though no evidence has yet been brought forward which 

 would justify belief in the transmissibility of acquired characters, 

 there can be no sort of question but that individuals do under- 

 go modification in this or that direction, as a consequence of 

 the malleability, so to speak, of such organs or tissues as are 

 subjected to particular stimuli. And some very striking facts 

 on this head have recently been put on record with regard to 

 the colours of certain birds, facts which go far to show that 

 such acquisitions during the life-time of an individual are not 

 transmitted to its offspring. 



To begin with, it is well known that many brilliantly coloured 

 birds become more or less pallid in captivity. This is especially 

 noticeable in the case of the American Rosy Flamingo {Phceni- 

 copterus ruber'). These birds invariably lose their colour in 

 confinement and become almost white. This pallor, it has been 

 shown, is due not to the reaction of an unfavourable climate, 

 but is intimately associated with the metabolism of the body, 

 a fact which has been demonstrated by experiment. Mr. 

 Beebe, the Curator of the Zoological Gardens of New York, ap- 

 pears to have been the first to demonstrate this point. " In 

 captivity," he remarks, "these birds [American Flamingoes] 

 fade out moult by moult, until they become almost white, like 

 the European species. By mixing with their food a quantity 

 of some strong but harmless dye I have had them either retain 

 their original colour for years, or at least the fading process has 

 been appreciably lessened." In the Gardens of the Zoological 

 Society of London this experiment has been carried to a yet 

 more satisfactory ending, for in place of " strong but harmless 

 dye" these birds were turned out into a paddock where they 

 had free access to a large pond well-stocked with small Crustacea, 

 a diet which quickly restored the lost hues. This is of particular 



