13 



SCIENTIFIC SIDE-LIGHTS 



Adaptation 

 Adaptations 



the unsubdued tribe of the Guaranes, at the 

 mouth of the Orinoco northward of the 

 Sierra de Imataca. When they increased in 

 numbers and became overcrowded, it is said 

 that, besides the huts which they built on 

 horizontal platforms supported by the 

 stumps of felled palm-trees, they also in- 

 geniously suspended from stem to stem 

 spreading mats or hammocks woven of the 

 leaf-stalk of the Mauritia, which enabled 

 them, during the rainy season, when the 

 Delta was overflowed, to live in trees in 

 the manner of apes. These pendent huts 

 were partly covered with clay. The women 

 kindled the fire necessary for their culinary 

 occupations on the humid flooring. As the 

 traveler passed by night along the river, his 

 attention was attracted by a long line of 

 flame suspended high in the air, and ap- 

 parently unconnected with the earth. The 

 Guaranes owe the preservation of their phys- 

 ical, and perhaps even of their moral inde- 

 pendence, to the loose marshy soil, over 

 which they move with fleet and buoyant 

 foot, and to their lofty sylvan domiciles; a 

 sanctuary whither religious enthusiasm 

 would hardly lead an American stylite. 

 HUMBOLDT Views of Nature, p. 12. (Bell, 

 1896.) 



63. ADAPTATION TO LIFE-WORK 



Teeth of Beaver Self -sharpening. The 

 amazing facility the beaver possesses for 

 felling trees is due to the power of its jaws 

 and teeth. Of these there are, as in the 

 aye-aye, two large cutting teeth above and 

 two below, separated by a toothless inter- 

 space from the grinding teeth behind them. 

 Each cutting tooth is protected in front by 

 a coating of very dense enamel, so that at 

 its summit it wears away less quickly in 

 front than behind, and thus a sharp, chisel- 

 like cutting edge is constantly preserved. 

 MIVART Types of Animal Life, ch, 12 p 

 352. (L. B. & Co., 1893.) 



64. ADAPTATION TO SEASON 



Grouse Provided with Snowshoes in Winter. 

 By far the best instance of modification 

 in the structure of the feet is furnished by 

 grouse. ^ It is an unusual case of seasonal 

 adaptation in form. During the summer 

 the toes of grouse are bare and slender, but 

 as these birds are largely ground-haunters, 

 and most of them inhabit regions where the 

 snowfall is heavy, the toes in winter acquire 

 a comblike fringe on either side. Practi- 

 cally, therefore, grouse don snowshoes in 

 the fall, and wear them until the following 

 spring. CHAPMAN Bird-Life, ch. 2 p 27 

 (A., 1900.) 



65. ADAPTATION TO TWO ELE- 

 MENTS AT ONCE Fish with Divided Eye. 

 Mr. Agassiz was especially interested in 

 seeing alive for the first time the curious 

 fish called " tralhote " by the Indians, and 

 known to naturalists as the Anableps te- 

 trophthalmus. This name, signifying " four- 

 eyed," is derived from the singular struc- 

 ture of the eye. A membranous fold en- 



closing the bulb of the eye stretches across 

 the pupil, dividing the visual apparatus into 

 an upper and lower half. No doubt this 

 formation is intended to suit the peculiar 

 habits of the Anableps. These fishes gather 

 in shoals on the surface of the water, their 

 heads resting partly above, partly below the 

 surface, and they move by a leaping motion 

 somewhat like that of frogs on land. Thus, 

 half in air, half in water, they require eyes 

 adapted for seeing in both elements, and the 

 arrangement described above just meets 

 this want. AGASSIZ Journey in Brazil, ch. 

 4, p. 143. (H. M. & Co., 1896.) 



66. ADAPTATION TO USE THROUGH- 

 OUT NATURE Darwinism Involves a New 

 Teleology. Adaptation to use, altho the 

 very essence of Darwinism, is not a fixed 

 and inflexible adaptation, realized once for 

 all at the outset; it includes a long pro- 

 gression and succession of modifications, ad- 

 justing themselves to changing circum- 

 stances, under which they may be more and 

 more diversified, specialized, and in a just 

 sense perfected. Now, the question is, does 

 this involve the destruction or only the re- 

 construction of our consecrated ideas of 

 teleology? Is it compatible with our seem- 

 ingly inborn conception of nature as an or- 

 dered system? Furthermore, and above all, 

 can the Darwinian theory itself dispense 

 with the idea of purpose, in the ordinary 

 sense of the word, as tantamount to de- 

 sign. ASA GRAY Darwiniana, art. 13, p. 

 358. (A., 1889.) 



67. ADAPTATIONS IN BIRD-STRUC- 

 TURE CUMULATIVE All Converged on the 

 Power of Flight Not Less Designed Be- 

 cause a Grototh. Now if, in examining the 

 structure of a typical bird, we find evi- 

 dences of " design " in the wonderful adap- 

 tation of its clothing of feathers alike to 

 keep in the warmth of the body, and to sus- 

 tain it in its flight through the air in that 

 organization of its heart and lungs which 

 enables them to keep up the energetic cir- 

 culation and respiration required for the 

 maintenance of a high standard of muscu- 

 lar activity in those arrangements of the 

 skeleton and muscular apparatus which give 

 support and motion to the expanded wings 

 in the adaptation of the eye to that acute 

 and far-ranging vision which is needed for 

 the guidance of its actions and in many 

 other provisions I might enumerate I af- 

 firm, without any doubt otf your assent, that 

 this evidence is not in the least degree in- 

 validated by the discovery that the germ- 

 particle is not a miniature bird, but a pro- 

 toplasmic " jelly-speck." In its capacity for 

 "evolution" into the complete type, the 

 germ-particle is just as much " potentially " 

 the bird as if it could become one by merely 

 swelling out. CARPENTER Nature and Man, 

 lect. 15, p. 432. (A., 1889.) 



68. ADAPTATIONS MANIFOLD IN 



NATURE Owe Part Serves Many Purposes. 

 Altho an organ may not have been originally 



