124 THE NAUTILUS. 



sixty-three years ago. Forces capable of changing habitat and habit 

 might change form and characteristics. 



My method in collecting is to traverse the beaches and from dead 

 or broken fragments of shells, observation of tide currents, eddies, 

 and prevailing winds, mark out probable stations at low water or 

 beyond. The method is seldom wrong and leads to live specimens, 

 either for wading or dredging, in shortest time. 



Some species in Panama Bay have gone to other stations. Some 

 have disappeared. Nearly all have sought deeper water and stay 

 there. 



Very solid volcanic rock, some of it nearly pure iron, is continu- 

 ous from two miles west of Panama City to Taboga Island, fourteen 

 miles. The Canal runs through part of it, and over the rest of this 

 strata. Heavy dynamite blasts on the main land arid on the islands 

 in the Bay where Canal fortifications are to make another Gibraltar, 

 can be felt distinctly at Taboga, too faraway to be heard, sometimes. 

 These concussions are frequent, occurring many times a day. A 

 breakwater extends from the mouth of the Canal to the island forti- 

 fications. This breakwater is two miles long, and all day long train- 

 loads of dynamited rock are dumped into the waters of the Bay on 

 either side. It is possible that four years of concussion and waters 

 more or less poisoned by nilroglycerene, plus the sewerage of Pan- 

 ama, may have destroyed food and driven the species to new stations, 

 to deeper water, or worse, destroyed many of them. The volcanic 

 reef ends abruptly a mile out and the water suddenly deepens to 

 thousands of feet. At Taboga the conditions are more favorable 

 and there is superb collecting ground, but even there low tide does 

 not expose the live specie? to any encouraging extent. The infer- 

 ence that all Panama species near the Canal have sought deeper 

 water is justified. 



There is a big suction dredge at Balboa near the mouth of the 

 Canal. This dredge takes up everything from bed rock to top sand 

 and sends a twelve-inch stream of water, mud, and millions of shells 

 (seldom alive), a mile or two inland to make new land. Most of 

 these shells have not been dead long, some are semi-fossil. There 

 is fine collecting at the end of that pipe. But specimens taken there 

 indicate wholesale destruction of molluscan life at the mouth of the 

 Canal. 



The most interesting " station " however on the Isthmus is in 



