TIME AND CHANGE 



climbing vines find their support, because in the 

 same blind way they feel in all directions. Plants 

 and animals and races of men grope their way to 

 new fields, to new powers, to new inventions. 



Indeed, how like an inventor Nature has worked, 

 constantly improving her models, adding to and 

 changing as experience would seem to dictate! She 

 has developed her higher and more complex forms 

 as man has developed his printing-press, or steam- 

 engine, from rude, simple beginnings. From the 

 two-chambered heart of the fish she made the treble- 

 chambered heart of the frog, and then the four- 

 chambered heart of the mammal. The first mam- 

 mary gland had no nipples; the milk oozed out and 

 was licked off by the young. The nipple was a great 

 improvement, as was the power of suckling in the 

 young. 



Experimenting and experimenting endlessly, tak- 

 ing a forward step only when compelled by neces- 

 sity, — this is the way of Nature, — experimenting 

 with eyes, with ears, with teeth, with limbs, with 

 feet, with toes, with wings, with bladders and lungs, 

 with scales and armors, hitting upon the back- 

 bone only after long trials with other forms, hitting 

 upon the movable eye only after long ages of other 

 eyes, hitting on the mammal only after long ages 

 of egg-laying vertebrates, hitting on the placenta 

 only recently, — experimenting all around the circle, 

 discarding and inventing, taking ages to perfect 



34 



