284 THE SEASON WHY. 



" They that go down to the sea in great ships, that do business in great waters 

 these see the works of the Lord, and his wonders in the deep." PSALM cvn. 



night, but it is, nevertheless, beautifully adapted for the purpose 

 stated, because the male is a night-flying insect, and never ventures 

 abroad by day. 



There exists some difference of opinion between naturalists upon the uses of 

 the light of a glow-worm ; there are some who doubt that it is exhibited to 

 attract the flying insect. The objectors, however, offer no explanation of the 

 luminous properties of the worm. Sir Charles Bell says the preponderance of 

 tlie argument is decidedly in favour of the explanation we have given. 



1129. Why does not the iris of the fish's eye contract ? 

 Because the diminished light in water is never too strong for 



the retina. 



1130. Why is the eye of the eel covered with a transparent 

 horny covering ? 



Because, as the eel lives in holes, and pushes its head into mud, 

 and under stones, &c., it needed such a covering to defend the eye. 



1131. Why is the whale provided with an eye, having 

 remarkably thick and strong coats ? 



Because, when he is attacked by the sword-fish and the shark, he 

 is almost helpless against his enemies, as they fix themselves upon 

 his huge carcase. He therefore dives with them down to a depth 

 where the pressure of the water is so great that they cannot bear it. 

 The eye of the whale is expressly organised to bear the immense 

 pressure of extreme ocean depths, without impairing the sight. 



1132. Why have fishes no eye-lids? 



Because the water in which they swim keeps their eyes moist. 

 Eyelids would therefore be useless to them. 



1133. Why have fishes the power of giving their eye-balls 

 very sudden motion T 



Because, having no eyelids (such organs being unnecessary to 

 keep their eyes moist), they still need the power of freeing their 

 eyes from the contact of foreign matters ; and this is secured to 

 them by the power they have of giving the eye-ball a very rapid 

 motion, which causes reaction in the fluid surrounding it, and sweep* 

 the surface. 



This motion may frequently be seen in the eyes of fishes, in glass globes. 



