No. 3.J SEXUAL SELECTION IN SPIDERS. 13i» 



and when it is spread out the bird is very beautiful, and is 

 hardly surpassed by any of the Birds of Paradise. 



The Carunculated Paradise Pie (Paradigalla carunculata) 

 has neither marked plumes nor ruff. 



The Paradise Oriole (Sericulus aureus) is chiefly charac- 

 terized by a quantity of feathers of an intense glossy orange 

 color which cover its neck down to the middle of the back. 



Two of the Rifle Birds we know nothing of. 



Thus we see that while eleven out of the fifteen paradise 

 birds have plumes arising near the pectoral muscle, the whole 

 fifteen have plumes arising from other places — tail, upper and 

 under surface of body, head and neck ; and that while nine out 

 of the fifteen have their most important ornament on the 

 breast, six have their finest plumes on some other part of the 

 body. The conclusion is inevitable that there is no causal 

 relation between muscular development and ornamentation. 

 Indeed, so far as these birds are concerned, it seems to us that 

 Mr. Wallace's earlier opinion is best, and as he so clearly sums 

 up the evidence we quote him in full : 



" The successive stages of development of the colors and 

 plumage of the birds of paradise are very interesting, from the 

 striking manner in which they accord with the theory of their 

 having been produced by the simple action of variation, and 

 the cumulative power of selection, by the females, of those male 

 birds which were more than usually ornamental. Variations 

 of color are of all others the most frequent and the most strik- 

 ing, and are most easily modified and accumulated by man's 

 selection of them. We should expect, therefore, that the sexual 

 differences of color would be those most early accumulated and 

 fixed, and would therefore appear soonest in the young birds ; 

 and this is exactly what occurs in the paradise birds. Of all 

 variations in the fo7in of birds' feathers, none are so frequent as 

 those in the head and tail. These occur more or less in every 

 family of birds, and are easily produced in many domesticated 

 varieties, while unusual developments of the feathers of the 

 body are rare in the whole class of birds, and have seldom or 

 never occurred in domesticated species. In accordance with 



