394 LAWS OF MULTIPLICATION. 



ent on certain environing actions ; and severally having theii 

 moving equilibria sooner or later overthrown by one or other 

 of these environing actions ; we have next to consider in 

 what ways the environing actions are so met as to prevent 

 extinction of the species. There are two essentially different 

 ways. There may be in each individual a small or great 

 ability to adjust itself to variations of the agencies around 

 it and to a small or great number of such varying agencies 

 there may be little or much power of preserving the 

 balance of the functions. And there may be much or little 

 power of producing new individuals to replace those whose 

 moving equilibria have been overthrown. A few facts must 

 be set down to enforce these abstract statements. 



There are both active and passive adaptations by which 

 organisms are enabled to survive adverse influences. Plants 

 show us but few active adaptations : that of the Pitcher-plant 

 and those of the reproductive parts of some flowers (which do 

 not, however, conduce to self-preservation) are exceptional 

 instances. But plants have various passive adaptations ; as 

 thorns, stinging hairs, poisonous and acrid juices, repugnant 

 odours, and the woolliness or toughness that makes their leaves 

 uneatable. Animals exhibit far more numerous 



adjustments, both passive and active. In some cases they 

 survive desiccation, they hybernate, they acquire thicker 

 clothing, and so are fitted to bear unfavourable inorganic 

 actions ; and they are in many cases fitted passively to meet 

 the adverse actions of other organisms, by bearing spines or 

 armour or shells, by simulating neighbouring objects in colour 

 or form or both, by emitting disagreeable odours, or by having 

 disgusting tastes. In still more numerous ways they actively 

 contend with unfavourable conditions. Against the seasons 

 they guard by storing up food, by secreting themselves in 

 crevices, or by forming burrows and nests. They save them- 

 selves from enemies by developed powers of locomotion, taking 

 the shape of swiftness or agility or aptitude for changing 

 their media ; by their strength either alone or aided by wea- 



