66 EVENINGS AT THE MICROSCOPE 



appears, then the lips close again, and presently reopen, 

 and the tongue again performs its rasping. It is wonder- 

 ful to see. Perhaps not more wonderful than any other of 

 God's great works, never more great than when minutely 

 great; but the action and the instrument, the perfect way 

 in which it works, and the effectiveness with which the 

 vegetation is cleared away before it, all strike the mind 

 with more than usual force, as exhibitions of creative skill. 



As the Periwinkle moves along, mowing his sea-grass 

 as he goes, he carries before him two soft and flexible 

 horns, marked with zebra-like bands of black and white, 

 which he constantly waves about. These are organs of 

 some sense, probably of touch, and are therefore called 

 tentacles (or tryers); but they bear on their outer sides, 

 near the base, a pair of other organs, which are more 

 closely analogous to what we ourselves possess. You see 

 on each tentacle a little wart, which, when you look at it 

 with a lens, you perceive to have a round black glossy ex- 

 tremity. This is the eye. By careful dissection under the 

 microscope, we find it to contain a beautiful transparent 

 crystalline lens, with a thick and glutinous vitreous humor 

 adhering to it behind, bounded by a retina or curtain to 

 receive the optic image, and an optic nerve. 



But much more attractive you will find the eyes in this 

 little Scallop. It is a half-grown individual of what is 

 provincially known as the Squin (Pecten opercularis), much 

 prized for its delicate sapidity. Belonging to the bivalve 

 class of the Mollusca, the animal is enclosed within two 

 shallow shelly plates, concave internally, and convex ex- 

 ternally, which are united by a hinge, just as the works of 

 a watch are protected by the case. When the little creat- 

 ure is at its ease, as when the water is pure and clear, it 



