266 THE HARMONIES OF NATURE. 



being totally wanting in their whole race ; and as they are 

 neither exposed to extreme variations of light, nor to the contact 

 of dust, they generally also require no eyelid for their protec- 

 tion. In the common eel however, which bores cavities in the 

 sand and mud at the bottom of the water, the eye is supplied 

 with a hard and transparent membrane, which it can draw over 

 the pupil at pleasure, thus effectually guarding these organs from 

 injury. The eyeball of the herring is also defended by two vertical 

 and transparent folds of the skin ; and it is worthy of observation 

 that where these folds decussate one another at their inferior ex- 

 tremities, the anterior one overlaps the posterior so slight an 

 impediment to progressive motion as the contrary position 

 would have occasioned, having thus been foreseen and avoided. 



As the external senses of fishes give them but few lively and 

 distinct impressions, their pleasures are little varied ; but, on the 

 other hand, the painful impressions they receive from the ex- 

 ternal world are likewise circumscribed within narrower limits 

 than those which bound the sensations of the birds and quadru- 

 peds. Though often subject to the terrors of flight, they in their 

 turn enjoy the excitement of pursuit : and a life of liberty makes 

 them amends for the violent end to which they are generally 

 doomed. Many a domestic animal or captive bird would willingly 

 exchange its hard lot for the free life of the fish, who from the 

 greater simplicity of his structure, his want of higher sensibili- 

 ties, his excellent digestion, and the more equal temperature of 

 the element in which he lives, remains free from many of the 

 diseases which torment the higher animals. 



The affections of fishes are cold as themselves ; but, though the 

 vast majority evince no sign of parental affection, and abandon 

 their offspring to the mercy of the sea and their predatory 

 companions, from the instant that the ova are shed, yet some at 

 least show glimpses of that self-denying instinctive love for 

 their young which often beams forth in so touching a manner 

 among the birds or quadrupeds. 



Thus, to preserve his eggs from the voracity of his brothers, 

 the male stickleback collects the delicate fronds of water-plants 

 or bits of grass that have been blown into the river, and forms 

 them into a nest, the entrance of which he guards with the 

 most sedulous care repelling with tooth and prickles all other 

 sticklebacks that approach the nest. If the enemy is too power- 



