94 THE STORY-BOOK OF SCIENCE 



nimble paw whips the wisp of paper that one throws 

 before it. Another year, and it is a tom-cat that 

 patiently watches for mice or joins battle with its 

 rivals on the roof. But, whether a tiny creature 

 hardly able to open its little blue eyes, or a pretty 

 playful kitten, or a big quarrelsome tom-cat, it has 

 always the form of a cat. 



"It is otherwise with insects. The swallow-tail, 

 under its form of butterfly, is not first small, then 

 medium, then large. When, for the first time, it 

 opens its wings and takes flight, it is as large as it 

 ever will be. When it comes out from under-ground, 

 where it lived as a grub, when for the first time it 

 appears in the daylight, the June bug is such as 

 you know it. There are little cats, but no little swal- 

 low-tails nor little June bugs. After the metamor- 

 phosis, an insect is what it will be to the end.' 7 



' t But I have seen small June bugs flying round the 

 willows iii the evening, " objected Jules. 



"Those little June bugs are of a different kind. 

 They will always remain the same. Never will they 

 grow and become common June bugs, any more than 

 a cat would grow into a tiger, which it resembles so 

 much. 



"The grub alone grows. At first very small on 

 coming out of the egg, little by little it acquires a 

 size in conformity with the future insect. It gathers 

 the materials that the metamorphosis will use, ma- 

 terials for the wings, antennae, legs, and all those 

 things that the larva does not have, but that the in- 

 sect must have. Out of what will the big green 

 worm that lives in dead wood, and must some day 



