752 



SCIENCE 



[N. S. Vol. XXXIII. No. 854 



to Boca Grande are composed of an oolitic lime- 

 stone — the Key West oolite, which has been so 

 recently elevated above sea-level that its upper 

 surface still shows sun-cracks. The Marquesas and 

 the Tortugas keys are composed of the commin- 

 uted, calcareous tests of organisms. 



The geologic activity of mangroves in convert- 

 ing shallow submarine banks into land areas was 

 described and illustrated by lantern slide photo- 

 graphs. The fruit of these plants, which is a pod 

 about six to nine inches long, falls into the water 

 and catches on the soft ooze of shallow banks, 

 where the young plants begin to grow, and after 

 developing a tangle of roots below and a tangle 

 of branches above the level of the water, catch 

 and retain any drifting debris. 



The speaker then pointed out how fossil corals 

 were utilized in ascertaining the depth and tem- 

 perature conditions under which geologic forma- 

 tions containing the remains of these organisms 

 were deposited. The restriction of reef-forming 

 corals to shallow water and regions of high tem- 

 perature, and the existence of a different fauna at 

 depths below 100 fathoms and in regions of cooler 

 temperature, were pointed out. 



Dr. Vaughan then briefly outlined the study of 

 the Florida corals, which he is conducting under 

 the auspices of the Carnegie Institution of Wash- 

 ington, with reference to various factors that de- 

 termine habitat and influence variation. He 

 showed that within the shallow water area of 

 southern Florida there are several different faunal 

 groups of corals that live under different condi- 

 tions. There are the reef corals proper, largely 

 of massive type, that grow on the barrier reef. 

 Other corals, either of more fragile form of 

 growth with a weaker basal attachment, or with 

 ability to wdthstand deposits of sUt over their 

 upper surface, live on the flats protected from 

 ocean breakers. Other corals of a fragUe habit 

 of growth live in channels where they have a con- 

 tinuous supply of pure water and are protected 

 from the breakers. More fragile corals grow at 

 the outer foot of a reef beneath the level of the 

 pounding of the breakers than on the reef proper. 

 The forms that grow at the outer foot of the reef 

 are to some extent similar to those that grow in 

 the channels or along the margin of channels pro- 

 tected from the pounding of the breakers. 



The subject of the rate of growth of corals was 

 briefly reviewed and the results of the investiga- 

 tions of Professor J. Stanley Gardiner in the 

 Maldive Islands were given. Professor Gardiner 

 there obtained a eoUeetion of corals none of which 



could have been more than three years of age, and 

 on the basis of these observations estimated that 

 the coral reef might increase one fathom in sixty 

 years. The observations of Gardiner are weak in 

 that he did not definitely know the age of the indi- 

 vidual specimens he obtained. 



Dr. Vaughan has at present about 200 different 

 coral colonies on which he is making annual meas- 

 urements to determine the growth rate. The colo- 

 nies comprise the various conditions under which 

 shallow-water corals grow around the Tortugas, so 

 that the investigations when completed will give 

 the growth rate for each species investigated, and 

 the variation in growth of each species in accord- 

 ance with the conditions under which it lives in 

 nature. The results of the observations at present 

 indicate that the rate of growth of corals is much 

 more rapid than was previously anticipated, so 

 that in a general way the opinions of Professor 

 Gardiner are substantiated. 



The technique of obtaining specimens for plant- 

 ing was briefly described. Besides those colonies 

 that are naturally growing on the reefs or in other 

 localities a number of specimens have been aflSxed 

 by hydraulic cement to tUes, and the tiles have 

 been planted on the heads of iron stakes driven in 

 selected localities. The tiles can be removed from 

 the stakes, measured and photographed at desired 

 intervals. 



Dr. Vaughan also described the technique of 

 rearing coral larvs and the planting of the afiSxed 

 young. The larvse are obtained from living corals 

 brought into the laboratory and kept in jars of 

 water. The planulse are then pipetted into a jar 

 containing sea-water and a tile on its bottom. 

 After the planulse have settled the tile is then 

 planted. Some of the tiles with attached larvae 

 were affixed to iron stakes in the sea and others 

 were attached to the bottom of a floating livecar. 

 It has been ascertained that a Favia planula may 

 attain a size of 9 mm. in diameter within a period 

 of seven months. 



The duration of the free-swimming larval stage 

 of corals has been carefully studied in order to 

 ascertain the possibilities of drift by ocean cur- 

 rents. The period varies from three or four days 

 to three weeks — periods of ten to twelve days are 

 common. These observations have definitely shown 

 that it is possible for coral larvse to be drifted 

 great distances by oceanic currents if the tempera- 

 ture conditions are favorable. 



D. E. Lantz, 

 Recording Secretary 

 April, 1911 



