318 The Study of Animal Life PART iv 



degrees. There may be direct results, rapid parries after 

 thrusts, or the results may be indirect ; they may affect the 

 organism visibly in the course of one generation, or only 

 after several have passed. 



Some animals are more susceptible and more plastic 

 than others. Young organisms, such as caterpillars and 

 tadpoles, are more completely in the grasp of their environ- 

 ment than are the adults. Thus Treviranus, who believed 

 very strongly in the influence of surroundings, distinguished 

 two periods of vita minima in youth and in old age 

 during which external conditions press heavily, from the 

 period of vita maxima in adult life when the organism 

 is more free. To some kinds of influence, e.g. mechanical 

 pressures, passive and sedentary organisms such as sponges, 

 corals, shell-fish, and plants, are more susceptible than are 

 those of active life. And it is during a period of quiescence 

 that surrounding colour tells on the sensitive caterpillars. 



3. Our own Environment. The human organism, like 

 any other, may be modified by its environment, for we 

 lead no charmed life. Those external influences which 

 touch body and mind are to us the more important, since 

 we have them to some extent within our own hands, and 

 because our lives are relatively long. Even if the changes 

 thus wrought upon parents are not transmissible, it is to 

 some extent possible for us to secure that our children grow 

 up open to influences known to be beneficial, sheltered from 

 forces known to be injurious. 



As the influence of surroundings is especially potent on 

 young things such as caterpillars and tadpoles all care 

 should be taken of the young child's environment during 

 the earliest months and years, when the grip that externals 

 have is probably much greater than is imagined by those 

 who believe themselves emancipated from the tyranny of 

 the present. 1 



As passive organisms are more in the thrall of their 

 surroundings than are the more active, we feel the import- 

 ance of beauty in the home, that the organism may be 



1 Cf. Matthew Arnold's poem, " The Future," and Walt Whitman's 

 " Assimilations." 



