208 THE WORLD OF LIFE 



than twice the length of the bird's body, and having, on one 

 side only of the midrib, a series of leaf-shaped thin horny 

 plates of a beautiful light-blue colour on the upper surface, 

 contrasting in a striking manner with the purple black, ochre 

 yellow, and rusty red of the rest of the plumage. 



In the comparatively small number of birds-of -paradise 

 now known, we have a series of strange ornamental plumes 

 w^hich in their shape, their size, their colours, and their point 

 of origin on the bird, exhibit more varietv than is found in 

 any other family of birds, or perhaps in all other known birds ; 

 and we can now better explain this by the assistance of Weis- 

 mann's law in a highly dominant group inhabiting a region 

 which is strikin^'lv deficient in animals wdiich are inimical to 

 bird-life in a densely forest-clad country. 



To this same principle we must, I think, impute that su- 

 perfluity of dazzling colour in many birds, but more especially 

 in many insects, in which it so often seems to go far beyond 

 usefulness for purposes of recognition, or as a warning, or a 

 distracting dazzle to an attacking enemy. 



Even in the vegetable kingdom this same law may have 

 acted in the production of enoiTQOus masses of flowers or of 

 fruits, far beyond the needful purpose of perpetuating the 

 species ; and probably also of those examples of excessive bril- 

 liancy of colour, as in the intense blues of many gentians, the 

 vivid scarlet of the Cardinal lobelia, or the glistening yellow 

 of many of our buttercups. It is quite possible, therefore, 

 that to this principle of ^' germinal selection " we owe some 

 of the most exquisite refinements of beauty amid the endless 

 variety of form and colour both of the animal and the veg- 

 etable world. 



We may also owe to it the superabundant production of sap 

 which enabled the early colonists of America to make almost 

 imlimited quantities of sugar from the '^ sugar maple." 

 Each tree will yield about four pounds of sugar yearly from 

 about thirty gallons of sap ; and it is stated by Lindley that a 

 tree wull yield this quantity for forty years without being at 



