4o8 



THE POPULAR SCIENCE MONTHLY 



swarming is not due to tidal influ- 

 ences, and now the great question is 

 — what does cause this remarkable 

 response, for it appears to be some 

 form of energy to which we aie 

 ourselves not sensitive. 



Dr. T. Wayland Vaughan, of 

 Washington, finds that the line of 

 the Florida Keys from Soldier's 

 Key to the southeastern corner of 

 Big Pine Key is composed of ele- 

 vated coral-reef rock. The northern 

 end of Soldier's Key and all keys to 

 the northward of it are composed of 

 quartz-bearing sands mingled with 

 broken shells. The keys from Key 

 AVest to Big Pine Key, with the ex- 

 ception of the southeastern corner 

 of the latter, are composed of lime- 

 stone mud which long ago was ele- 

 vated above the sea and changed 

 into rock, so that now one sees a 

 net-work of old mud-cracks in the 

 rocky floor of the pine forest. On 

 the continental side of the line of coral-reef keys and extending trans- 

 versely to them are long shoals formed by the settling of lime mud in 

 the slack water between the currents which flow in and out with the 

 tides through openings between keys. These shoals become covered 

 with mangroves, and thus finally elevated above the surface of the sea. 

 There are many other interesting geological observations made by Dr. 

 Vaughan which limitations of space prevent us from reviewing. 



In addition to his studies of the geology of the reef's, he is making 



Fig. 10. 



The Atlantic Palolo Wokm, 

 Eunice fucata. 



Fig. 11. The Ghost Crab, Ocypoda armaria. Photographed by Dr. R. P. Cowles. 



