DIRECT INTERFERENCE BY MAN. 
291 
Food is known to determine with precision the 
habitats of many kinds, though as shown under 
the head of Primary Laws it has not that amount 
of power supposed by some, and many situations 
producing the required pabulum do not produce 
the animals so dependent, and where, if removed, 
they thrive well. Our Bulimus fasciatus and 
Helix virgata which seemingly need maritime 
localities from some preference of food, do not oc¬ 
cur universally all along the coast though the 
vegetation is seemingly uniform in character, but 
are collected together in parties at certain spots. 
Cyclostoma elegans occurs at Berry Head, but is 
absent from the loose tracts round Plymouth. 
Man conducts a warfare against certain animals 
which he finds or supposes to be prejudicial to his 
interests. In some cases, as where by our agricul¬ 
tural operations, &c. animals have been permitted 
to multiply more than their natural enemies would 
have allowed, our destruction of their superfluous 
number is justifiable; and likewise in the case of 
such creatures whose lives and actions are incom¬ 
patible with our security and operations, extirpation 
is demanded. Many of those animals however, 
consigned to unlimited destruction, form important 
links in the chain of creation, and in consequence 
their deficiency w r ill cause alterations of various 
kinds in the proceedings of those other creatures 
with whom they were associated in the general 
scheme and polity of nature. The merciless destruc¬ 
tion of our rapacious birds by gamekeepers and 
others must permit a vast accumulation of those 
species of smaller animals on which they feed, and 
in consequence, a more general and unnatural dis¬ 
persion. A consideration therefore of the operations 
of man, whether as respects his agricultural or his 
other improvements and refinements, or whether as 
regards his hostilities to the animal creation, is 
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