332 THE REASON WHY. 



"Thou hast set all the borders of the earth: thou hast made summer and 

 winter." PSALM LXXIT. 



1305. Why are the perfect insects said to be in the 

 "nymph" state? 



Because their joyful existence, and their beautiful forms, give 

 them a fancied resemblance to the nymphs of the heathen 

 mythology. The nymphs were supposed goddesses of the moun- 

 tains, forests, meadows, and waters. 



This term has generally, but very improperly, been also applied to the pupa 

 state, so that pupa, chrysalis, and nymph have all been employed to represent 

 one state. This is obviously an error, as there is nothing in the condition of the 

 pupa or chrysalis that can at all accord with the mythological idea of a nymph, 

 and which, in reference to the beautiful and joyous fly, finds a much truer 

 application. 



CHAPTER LXVIL 



1306. Whence does the snail obtain its shell ? 



Young snails come from the egg with a shell upon their 

 lacks. 



1307. Sow does the shell grow with the increase of size 

 of the animal ? 



The soft slime which is yielded by the body of the animal, 

 hardens upon the orifice of the shell, and thus increases its size. 



Fig. 80. COMMOW GABDEJf SNAI1. 



1308. Why is the shell spiral ? 



Partly because of its original formation ; but also because, at the 

 ihell grows, the opening is elongated, and thrown up, causing tho 



