292 DARWINISM chap. 



springs from a very small area on the side of the breast. Mr. 

 Frank E. Beddard, who has kindly examined a specimen for 

 me, says that " this area lies upon the pectoral muscles, and 

 near to the point where the fibres of the muscle converge 

 towards their attachment to the humerus. The plumes arise, 

 therefore, close to the most powerful muscle of the body, and 

 near to Avhere the activities of that muscle Avould be at a 

 maximum. Furthermore, the area of attachment of the plumes 

 is just above the point where the arteries and nerves for the 

 supply of the pectoral muscles, and neighbouring regions, 

 leave the interior of the body. The area of attachment of 

 the plume is, also, as you say in your letter, just above the 

 junction of the coracoid and sternum." Ornamental plumes 

 of considerable size rise from the same part in many other 

 species of paradise birds, sometimes extending 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 move- 

 ment, indicating a surplus of vitality, which is able to manifest 

 itself in the development of these accessory plumes.^ 



In a quite distinct set of birds, the gallinacere, Ave 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 loAver 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, 



1 For activity and pugnacity of liummiug-birds, see Trojiical Nature, jjp. 

 130, 213. 



