ii TIME AS A FACTOR 123 



seeing that in all cases of ordinary 

 generation, and conspicuously in a thou- 

 sand cases of metamorphoses among 

 the lower creatures, the full develop- 

 ment of germs takes a very short time 

 indeed. In the case of some birds, a 

 fortnight or three weeks at the outside 

 is sometimes enough of time wherein to 

 develop, from an egg, a complete fowl 

 with legs, and wings, and instincts, all 

 ready-made to lead an adult and inde- 

 pendent life. In frogs and toads the 

 time of hatching varies from three days 

 to three weeks. In some insects a few 

 hours is enough to produce a creature 

 very highly organised, with many special 

 adaptations. In other numberless cases, 

 a living creature, already leading a separ- 

 ate life, is put to sleep within an external 

 case or shell, and, in that state of sleep, 

 is radically transformed in all its organs, 

 and comes out in a few days an entirely 



