A Good Habit Gone Wrong 



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ture's odor penetrate the dull nostrils of the foe, 

 and an examination follow, if the prey had reso- 

 lution enough to continue its quiet position, 

 so that it would appear to be dead, even with a 

 great dinosaur nose poking at it, it would prob- 

 ably be left untouched, for, as a rule, land rep- 

 tiles do not feed upon carrion. 



An ability of this self -preserving kind would 

 be almost a corollary of existence under the cir- 

 cumstances in which the Mesozoic opossums 

 found themselves ; the habit would be of a nature 

 most likely to be advanced by natural selection ; 

 and in the course of the immensely long time 

 available for producing the effect the practice 

 would become thoroughly ingrained into opos- 

 sum nature. But after a while the great stupid 

 reptiles died out and were gradually replaced 

 by hunters and foes alert in perception, quick- 

 witted and active. An adaptive, plastic sort of 

 animal would have shaped habits and structure 

 to the new circumstances as they arose : but the 

 opossum nature is not of that kind, perhaps 

 no other has been physically so inflexible; and 

 along with its unchanging body has gone a 



$ 139 ** 



