150 REPORTS OF INVESTIGATIONS AND PROJECTS. 



dominant in the hybrid larvae. But if sea- water be treated with acetic acid 

 or HCI, so as to reduce but not destroy its alkalinity to litmus, the Toxop- 

 neustes parent becomes dominant. 



Professor Tennent has thus shown that dominance, or prepotency, may be 

 altered by changes in the environment, and his results are comparable with 

 those of Tower in altering dominance in beetles through changes in tempera- 

 ature and humidity, or with those of MacDougal in the artificial production 

 of new forms of plants through changes induced by external agents upon the 

 germ-cells. His paper upon this interesting subject is being prepared for 

 publication by the Carnegie Institution of Washington. 



Prof. Aaron L. Treadwell has made a study of the swarming habits of the 

 Atlantic palolo-worm Eunice fucata, which swims for breeding purposes 

 upon the surface of the sea within three days of the time of the last quarter 

 of the July moon, and he has discovered that if the rocks containing the 

 worms be placed in a dark chamber upon the day preceding the night of the 

 swarm the worms may still swarm. Hence, contrary to Mayer's supposition, 

 the presence of moonlight is not necessary for the swarming reaction. Pre- 

 vious studies at Tortugas have shown that the swarming is not due to tidal 

 influences. 



Dr. T. Wayland Vaughan finds that the line of the Florida Keys from 

 Soldier's Key to the southeastern corner of Big Pine Key is composed of 

 elevated coral-reef rock. The northern end of Soldier's Key and all keys 

 to the northward of it are composed of siliceous sands with some comminuted 

 shells. The keys from Boca Grande to Big Pine Key, with the exception of 

 the southeastern corner of the latter, are composed mainly or in part of 

 oolitic rock, which in places shows mud-cracks. On the continental side of 

 the line of the coral-reef keys, extending transversely to their trend, are long 

 shoals formed by deposition of mud in the slack-water between the currents 

 which flow in and out with the tides through the 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 reefs. Dr. Vaughan is mak- 

 ing the most accurate and extensive investigation of the natural associations, 

 habits, rate of growth, and constitution of coral reefs ever attempted by any 

 naturalist. He is rearing corals from the planula, and observing their rate of 

 growth as well as studying the growth-rate of many coral-heads found living 

 upon the reefs or in the moat of Fort Jefferson. Years must elapse before 

 the results of these studies will be ready for publication, but he has already 

 discovered that under favorable conditions the rate of growth of corals is 



