CHAPTER VI 



Propagation (continued) — Nest-making not purely a bird-habit 

 — ^Eggs laid without nests — Types of nests — ^Parasitic nesting 

 — ^Parasitic layers, like Cuckoos and Cow-birds — ^Degrees of 

 'development of parasitic instinct. 



Birds are not alone in incubating their eggs any 

 more than in laying eggs at all ; for pythons among 

 snakes incubate their eggs, coiling round them 

 and undergoing a rise of temperature, while the 

 Echidna of Australia, one of the only two egg-laying 

 mammalian types — the other oviparous beast being 

 the Duck-billed Platypus-^carries her single egg in 

 a temporarily formed pouch. The two eggs of the 

 Platypus are laid in her burrow. 



Neither is nest-making confined to birds, for, 

 putting aside the extraordinary structure made by 

 many insects, we have nest-makers among the 

 vertebrates in the persons of many fish— including 

 our little stickleback — in some tropical frogs, and 

 in numerous beasts from the gorilla to the harvest- 

 mouse. These points are worth mentioning, be- 

 cause some naturalists theorize about birds' nests 

 as if nest-making were a special bird habit, whereas 

 for all we know the particular reptile which pre- 

 ceded the first definite bird may have been a nest- 

 builder already. 



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