78 UNIVERSAL EVOLUTION 



natural selection. Those organisms which die prema- 

 turely, are the unadapted, the unfit. The strong, and 

 adapted, are the ones which survive. The old, who 

 die, are those who were adapted, and fit at one time, 

 but have become unfit, by the changes in their struc- 

 ture. 



VIGOR IN THE OFFSPRING. All the methods of nature 

 in reproduction are those that will produce vigor in the 

 offspring, so that the strong only are perpetuated. In 

 this way, also, a certain per cent of the young are found 

 to vary from their parents in certain organs and char- 

 acteristics. These are termed variations. If these are 

 found upon trial, to be beneficial to the organisms, 

 possessing them, in their efforts for capturing food, for 

 self defense, or procreation, then naturally these varia- 

 tions are preserved, and in many instances are inherited 

 by the offspring. The latter may also have additional 

 variations useful to them, added to those inherited from 

 their parents, which still further aid them in the 

 struggle for existence. 



The accumulation of useful heritable variations thus 

 occurring, generation after generation, will finally pro- 

 duce a form so different in its anatomy and physiology, 

 from the original parents of the first variation, that a 

 new species results. One test of a new species is, that 

 it is less likely to cross with other species than with its 

 own. However this may be, and there seem to be ex- 

 ceptions, the theory of natural selection of variations 

 in nature in the survival of the fittest, is the most 

 reasonable one to account for the origin of species. 



Given heredity and variation, or as Haeckel calls 

 it, adaptation, then natural selection simply means, the 

 continuation of the favorable, and the dying out of the 

 unfavorable. Among the lower organisms especially, 



