CHAPTER IV 



SHIFTS FOR A LIVING 



I. Insulation — 2. Concealment — 3. Parasitism — 4. General Re- 

 semblance to Surroundings — 5, Va7-iable Colouring — 6. Rapid 

 Change of Colour — 7. Special Protective Resemblance — 8. 

 IVarning Colours — 9. Mimicry — lo. Masking — 11. Com- 

 bination of Advantageous Qualities — 12. Surrender of Parts 



Granting the struggle with fellows, foes, and fate, we are 

 led by force of sympathy as well as of logic to think of the 

 shifts for a living which tend to be evolved in such con- 

 ditions, and also of some other ways by which animals 

 escape from the intensity of the struggle. 



I. Insulation. — Some animals have got out of the 

 struggle through no merit of their own, but as the result 

 of geological changes which have insulated them from 

 their enemies. Thus, in Cretaceous times probably, the 

 marsupials which inhabited the Australasian region were 

 insulated. In that region they were then the only re- 

 presentatives of Mammalia, and so, excepting the " native 

 dog," some rodents and bats, and more modern imports, 

 they still continue to be. By their insulation they were 

 saved from that contest with stronger mammals in which 

 all the marsupials left on the other continents were 

 exterminated, with the exception of the opossums, which 

 hide in American forests. A similar geological insulation 

 accounts for the large number of lemurs in the island of 

 Madagascar. 



