128 Human Physiology. 



adapted to steamers; the fins which keep them from rolling; 

 air bladders which they expand when they wish to rise and 

 compress to sink; and their wonderful armour of beautiful 

 overlapping scales, are all familiar; but for special adaptations 

 let me point to the hammer-headed shark, with its eyes so 

 carried out that it can see in every direction, and those strange 

 instruments of war furnished to the sword-fish and the saw-fish. 



Fishes may seem stupid, cold-blooded creatures to us, but 

 how perfectly are they adapted to their conditions ; and their 

 mental qualities are not to be despised. How does the salmon 

 find his way through the pathless depths of the ocean back to- 

 his native river? Does the angler fish watch for his prey 

 because nature has provided him with a line and bait above 

 his head, or did line and bait grow there because he happened 

 to have a taste for angling? How came the electric eel by a 

 complete galvanic battery, and then to know how to use it to 

 stun his enemies or his prey? Unlike other batteries, this is 

 under the control of his will. He gives or withholds the shocks 

 as he pleases. Who taught the goby and stickleback to build 

 nests, watch over their eggs, and drive off intruders? Who 

 contrived the sucker of the sucker-fish, so that he could make 

 fast to a shark or other strong fleet swimmer and be carried 

 about like a barnacle? And why should the barnacle, which 

 at first swims about, lose his eyes when he has once made fast 

 to ship or timber, and has no further use for them? 



The common snail, with his house on his back, has teles- 

 copic eyes like a lobster, which he can draw back as one 

 pushes in the finger of a glove, elaborately-formed ears with 

 special auditory nerves, and in a cavity of each are minute 

 crystalline bodies in constant motion, vibrating, turning on their 

 axes, rushing with violent motion to the centre of their cell, 

 from which they are violently repelled. 



Serpents give us instances of design, or adaptation of means 

 to ends beyond the powers of chance variation, similar in some 



