126 SECRETS OF EARTH AND SEA 



recognition of the fact that the actual tendencies to varia- 

 tion — accumulated in the living substance of the various 

 stocks or lines of descent and handed on during an 

 immense succession of ages of change by hereditary 

 transmission — counts for more in the production of new 

 species and strange, divergent, even grotesque forms- of 

 both animals and plants than had been supposed. 



Undoubtedly selection or survival of the fittest mainly 

 accounts for the colouring and adaptive shaping of 

 living things, and so for those several great types 

 of modelling which arrest the eye and have excited 

 the interest of inquisitive man. But there seems to be 

 no justification for the assumption that in all cases a 

 variation — that is to say, an increase or a diminution 

 of the volume of some existing structure in proportion 

 to other coexisting structures in the body of a living 

 plant or animal — must be either favourable, that is, con- 

 ducive to survival, or injurious, that is, tending to the 

 defeat and destruction of its possessors or their race. On 

 the contrary, it is the fact that there are vast areas and 

 conditions related to countless myriads of living creatures 

 in which variations of those creatures of large and impos- 

 ing kind and degree are neither advantageous nor dis- 

 advantageous, but matters of absolute indifference, that is 

 to say, without any effect upon the preservation or survival 

 of their race or stock. Nature is far more tolerant than 

 some of us were inclined to assume. In certain restricted 

 conditions of competition and in regard to some special 

 structures and components which are often so minute and 

 obscure as to be not yet detected by that recent arrival, 

 the investigating biologist — though sometimes, fortunately 

 for him, large enough to jump to his eyes — it is undeni- 

 able that there must be a "survival" or "favouring" of 

 individuals presenting a variation in increase, or it may be 

 decrease, of this or that special feature of its " make-up " 



