136 PECKHAM. [Vol. 1, 



laterally in front, so as to form breast shields. They also occur 

 in many humming-birds, and in some sun-birds and honey- 

 suckers; and in all these cases there is a wonderful amount of 

 activity and rapid movement, indicating a surplus of vitality, 

 which is able to manifest itself in the development of these 

 accessory plumes. 



" In a qnite distinct set of birds, the gallinacefe, we find the 

 ornamental plumage usually arising from very different parts, 

 in the form of elongated tail-feathers or tail-coverts, and of ruffs 

 or hackles from the neck. Here the wings are comparatively 

 little used, the most constant activities depending on the legs, 

 since the gallinacese are pre-eminently walking, running and 

 scratching birds.* Now the magnificent train of the peacock — 

 the grandest development of accessory plumes in this order — 

 springs from an oval or circular area, about three inches in 

 diameter, just above the base of the tail, and therefore situated 

 over the lower part of the spinal column near the insertion of 

 the powerful- muscles which move the hind limbs and elevate 

 the tail. The very frequent presence of neck-ruffs or breast- 

 shields in the males of birds with accessory plumes may be 

 partly due to selection, because they must serve as a protection in 

 their mutual combats, just as does the lion's or the horse's mane. 

 The enormously lengthened plumes of the bird of paradise and 

 of the peacock can, however, have no such use, but must be 

 rather injurious than beneficial in the bird's ordinary life. 

 * * * * If we have found a vera causa for the ornamental 

 appendages of birds and other animals in a surplus of vital 

 energy, leading to abnormal growths in those parts of the 

 integument where muscular and nervous action are greatest, 

 the continuous development of these appendages will result 

 from the ordinary action of natural selection in preserving 

 the most healthy and vigorous individuals, and the still 

 further selective agency of sexual struggle in giving to the 

 strongest and most energetic the parentage of the next 

 generation." 



* Eight out of fifteen species of birds of paradise, altlioiigh they ai 

 , birds, have elongated and ornnraentnl tail-feathers. 



