112 SECRETS OF EARTH AND SEA 



stimulus of new environmental conditions has been com- 

 pared to that of the well-known pattern-producing toy 

 the kaleidoscope. The bits of glass, beads and silk which 

 you see in a kaleidoscope, forming by reflection in its 

 mirrors a beautiful and definite pattern, are changed 

 by a simple vibration caused by tapping the instrument 

 into a very different pattern, the coloured fragments 

 being displaced and rearranged. The apparent change 

 or variation is very great though produced by slight 

 mechanical disturbance, and the new pattern is altogether 

 without any special significance the fortuitous outcome 

 of a small displacement of the constituent coloured 

 fragments. We can imagine that similarly slight dis- 

 turbances of the organic molecules of the germ-plasm 

 may produce considerable and important variations in it 

 and the new growth to which it gives rise : and, further, 

 that these variations may prove to be either (i) injurious, 

 or (2) of life-saving value, or often enough (3) of no con- 

 sequence whatever although bulking largely in our human 

 eyes and thereby misleading our judgment of them. 



There is no reason to doubt that the same sequence of 

 events occurs in nature apart from man's interference. 

 Changes occur in the earth's surface, or the organism is 

 transported by currents of water or air into new condi- 

 tions. The germ-plasm is " disturbed," " shaken " or 

 " shocked " by those new conditions, and a variation, in 

 several structures and qualities of the offspring subse- 

 quently produced, follows. Then also follows the selec- 

 tion of one of the new varieties by survival of the fitter to 

 the new conditions into which the organism has been 

 transported or have developed in the region where it was 

 previously established. 



This process of germ-variation is obviously as necessary 

 and constant a feature of the living organism as is the 

 variation in the contour of land and sea and in the extent 



