Adaptation 



SCIENTIFIC SIDE-LIGHTS 



10 



black, washed or tinged with rhubarb yel- 

 low. Their black plumage would render 

 them conspicuous in the sunshine, but they 

 pass their lives in dense tropical forests, 

 where the sun at noon sheds only a gloomy 

 twilight. HUDSON Naturalist in La Plata, 

 ch. 18, p. 248. (C. & H., 1895.) 



47. White Coloration of 



Arctic Animals Protective. In the arctic 

 regions there are a number of animals 

 which are wholly white all the year round, 

 or which only turn white in winter. Among 

 the former are the polar bear and the 

 American polar hare, the snowy owl and the 

 Greenland falcon; among the latter the arc- 

 tic fox, the arctic hare, the ermine, and the 

 ptarmigan. Those which are permanently 

 white remain among the snow nearly all the 

 year round, while those which change their 

 color inhabit regions which are free from 

 snow in summer. The obvious explanation 

 of this style of coloration is that it is pro- 

 tective, serving to conceal the herbivorous 

 species from their enemies, and enabling car- 

 nivorous animals to approach their prey un- 

 perceived. WALLACE Darwinism, ch. 8, p. 

 130. (Hum., 1889.) 



48. ADAPTATION OF COLOR TO HAB- 

 ITS Brilliancy of Color Possible for Female 

 Birds in Protected Nests. There are con- 

 siderable numbers of birds in which both 

 sexes are similarly and brilliantly colored. 

 Such are the extensive families of the king- 

 fishers, the woodpeckers, the toucans, the 

 parrots, the turacos, the hangnests, the 

 starlings, and many other smaller groups, 

 all the species of which are conspicuously or 

 brilliantly colored, while in all of them the 

 females are either colored exactly like the 

 males, or, when differently colored, are 

 equally conspicuous. ... In all these 

 cases, without exception, the species either 

 nests in holes in the ground or in trees, or 

 builds a domed or covered nest, so as com- 

 pletely to conceal the sitting-bird. We have 

 here a case exactly parallel to that of the 

 butterflies protected by distastefulness, 

 whose females are either exactly like the 

 males, or, if different, are equally conspicu- 

 ous. WALLACE Darwinism, ch. 10, p. 188. 

 (Hum., 1889.) 



49. ADAPTATION OF DEVICES TO 

 CLIMATE Binding with Rawhide among the 

 Eskimos. The peoples of the world who live 

 north of the tree-line, and many who dwell 

 in more temperate zones, have discovered 

 the virtue of rawhide. The Eskimo spends 

 many hours in cutting out miles of raw- 

 hide string, or babiche, of all degrees and 

 sizes. This he uses in holding together not 

 only the parts of his implements, but in 

 manufactures of every kind. It is a mar- 

 velous substance. Frost that will snap 

 steel nails like glass has no effect upon it. 

 W 7 hen it is put on green and allowed to dry, 

 it shrinks nearly one-half, binding the parts 

 immovably. 



Further south, as well as in the Arctic 



region, the tough sinew is taken from the 

 leg of the deer. It is shredded as fine as 

 silk, spun into yarn, and then twisted or 

 braided into cord. This has no end of uses, 

 not only in tool making, but in all arts 

 where the greatest possible toughness and 

 pliability are demanded. It serves to make 

 a secure ferrule on the awl handle, to 

 strengthen the bow, to hold feather and 

 head on the arrow. It has an economic use 

 for every day in the year. MASON Origins 

 of Invention, ch. 2, p. 41. (S., 1899.) 



50. ADAPTATION OF FLOWERS TO 

 INSECTS Contrivances That Guide or Force 

 Visiting Insect to Fertilize Flower The 

 Labellum in Orchids. The labellum is by 

 far the most important of the external 

 envelopes of the flower. It not only se- 

 cretes nectar, but is often modeled into 

 variously shaped receptacles for holding 

 this fluid, or is itself rendered attractive so 

 as to be gnawed by insects. Unless the 

 flowers were by some means rendered at- 

 tractive, most of the species would be cursed 

 with perpetual sterility. The labellum al- 

 ways stands in front of the rostellum. and 

 its outer portion often serves as a landing- 

 place for the necessary visitors. In Epi- 

 pactis palustris this part is flexible and 

 elastic, and apparently compels insects in 

 retreating to brush against the rostellum. 

 In Cypripedium the distal portion is folded 

 over like the end of a slipper, and compels 

 insects to crawl out of the flower by one of 

 two special passages. In Pterostylis and a 

 few other orchids the labellum is irritable, 

 so that when touched it shuts the flower, 

 leaving only a single passage by which an 

 insect can escape. In Spiranthes, when the 

 flower is fully mature, the column moves 

 from the labellum, space being thus left for 

 the introduction of the pollen-masses at- 

 tached to the proboscis of a bumblebee. In 

 Mormodes ignea the labellum is perched on 

 the summit of the column, and here insects 

 alight and touch a sensitive point, causing 

 the ejection of the pollen-masses. The la- 

 bellum is often deeply channeled, or has 

 guiding ridges, or is pressed closely against 

 the column; and in a multitude of cases it 

 approaches closely . enough to render the 

 flower tubular. "By these several means 

 insects are forced to brush against the ros- 

 tellum. DARWIN Fertilisation of Orchids, 

 ch. 9, p. 275. (A., 1898.) 



51. ADAPTATION OF MEANS TO 

 ENDS Seeming Intelligent Choice on the Part 

 of Earthworms Intelligence Not Limited 

 by Size of Brain. To sum up, as chance 

 does not determine the manner in which ob- 

 jects are drawn into the burrows, and as the 

 existence of specialized instincts for each 

 particular case cannot be admitted, the 

 first and most natural supposition is that 

 worms try all methods until they at last 

 succeed ; but many appearances are opposed 

 to such a supposition. One alternative 

 alone is left, namely, that worms, altho 



