THE CONDITION OF WOMEN. 1+7 



individual differences are so overshadowed by the much more con- 

 spicuous resemblances due to heredity with which they compare 

 about as the green buds at the tips of the twigs of a large tree com- 

 pare with the hard wood of the trunk and branches, the growth of 

 previous years and they are so fluctuating and inconstant, that their 

 importance may easily escape attention. Careful observation shows, 

 however, that every characteristic may vary : those distinctive of the 

 class or order as well as those which mark the species or variety. The 

 variations may manifest themselves in the adult, or at any other 

 period in the life of the individual. Even the eggs have individuali- 

 ties of their own, and among many groups of animals the eggs of the 

 same parent, when placed under precisely similar conditions, may 

 differ in the rate and manner of development. Although most of 

 these individual differences are transient, and disappear within a few 

 generations, there can now be no doubt that those which tend to brino- 

 the organism into more perfect harmony with its environment, and 

 are therefore advantageous, may be established as hereditary features, 

 through the action of the law of the survival of the fittest ; and it is 

 hardly possible to over-estimate the value of the evidence which pale- 

 ontology and embryology now furnish to prove that all hereditary 

 characteristics, even the most fundamental, were originally individual 

 variations. 



The series of hereditary structures and fnnctions which makes up 

 the life of an organism is constantly being extended by the addition 

 of new features, which at first were individual variations, and are 

 gradually built into the hereditary life history. In this way newly 

 acquired peculiarities are gradually pushed further and further from 

 what may be called the growing end of the series, by the addition of 

 newer variations above them. It can also be shown that from time to 

 time the peculiarities at the other end of the series, the oldest heredi- 

 tary features, are crowded out of the life of the organism, and dropped, 

 so that an animal which is hisrh in the scale of evolution does not re- 

 peat, in its own development, all of the early steps through which its 

 most remote ancestors have passed. The series of hereditary charac- 

 teristics, thus growing at one end and fading away at the other, gradu- 

 ally raises the organism to new and higher stages of specialization, and 

 its evolution by variation and heredity may be compared with the 

 growth of a glacier. 



The slight individual differences are represented by the new layers of 

 snow added by the storms to the deposit which fills the valley in which 

 the glacier arises. The snows which are soon blown away are those 

 variations which, being of no use, soon disappear ; while the snow 

 which remains in the valley, and is gradually converted into ice, repre- 

 sents those individual differences which are seized upon by natural 

 selection, and gradually rendered hereditary and constant. The long 

 stream of ice stretching down to lower regions, and made up of the 



