THE MARVEL OF A TIDE 325 



nudged each very gently and then proceeded to crawl over 

 my foot where it examined minutely an old scar inflicted by 

 the sharp edge of an oyster shell years before. 



Life in this tide-swept land clung almost exclusively to the 

 rocks. The outer sand with its curving ridges was too com- 

 pletely unstable to house any permanent organisms. It was a 

 watery no-man's land, a barren sheet of white against a back- 

 ground of blue. However, in the temporary quiet of the full 

 flood, a number of fishes were deserting the rocks and making 

 short excursions into the open. With the exception of the 

 larger and more able types, few strayed any great distance. 

 The sergeant-majors, blueheads, and the demoiselles were re- 

 stricted to within eight or ten feet. Within this range they 

 seemed very confident, frequently passing within easy reach 

 of much larger forms. They knew that with a twist of a fin 

 they could dart into the safety of a crevice. The only small 

 forms that strayed with impunity into the open sand were the 

 trunkfish, which no doubt felt secure behind their solid casings 

 of jointed armor, and the porcupine fish, which are the nearest 

 things to a living pincushion except the sedentary sea urchins. 

 These were utterly without fear, and little wonder, for even 

 to touch one would be to invite a painful puncture. 



The open water was also inhabited by a small group of swell- 

 fishes, drab prickly fellows with gullets capable of tremendous 

 extension when they are alarmed. These fish are supposed to 

 be very stupid, yet in the Chesapeake Bay I have observed close 

 relatives of the West Indian forms attacking large blue crabs 

 in mass and biting with their sharp teeth through the crabs' 

 hard shells, a task that would be exceedingly dangerous if at- 

 tempted singly. No creature that is capable of such organized 

 action can be considered stupid. 



Most of the fish that patrolled the outer waters were large 

 carnivores that swept ceaselessly back and forth waiting for 



