592 vaughan: growth-rate of shoal-water corals 



for a critical study of the laws of growth rate. The proportion 

 of living tissue to the stony skeleton is relatively small and as the 

 skeleton after very young stages usually is not entirely covered 

 by the living soft parts, organisms may attach themselves to it 

 and increase its weight, or boring organisms may enter it, begin 

 its destruction, and decrease its weight. As many boring organ- 

 isms have calcareous tests, they destroy a part of the original 

 skeleton and add the weight of their own. Minute algae, as 

 Duerden has shown, bore into the skeleton and ramify through 

 it almost or quite to the boundary of the living soft parts. 

 Weights obtained from specimens cemented to discs are sub- 

 ject to all the sources of inaccuracy enumerated above and also 

 to the practical inability of restoring the disc to its initial con- 

 dition after affixing and planting a specimen, because of organ- 

 isms attaching themselves to its surface. These remarks make 

 it clear that the object of the investigation is not to make a 

 contribution to the laws governing growth-rate, although some 

 of the principles of growth-rate of some species have been as- 

 certained. The actual object of the investigation has been to 

 aid in understanding the relative amount of work stony corals 

 may do as constructional geologic agents, and especially in the 

 formation of those calcium carbonate structures designated 

 ''coral reefs." 



In order properly to evaluate corals as constructional agents, 

 the subject needs to be studied from at least five different view- 

 points, viz.: (1) In dealing with sediments uplifted above the 

 sea, the quantity of material contributed by corals and that 

 contributed by other agents must be estimated and the re- 

 spective proportions determined; (2) in coral reef areas, the 

 ratio of the area covered by corals to that not covered by them 

 should be estimated; (3) the relations of coral reefs to continuity 

 and discontinuity of marginal submarine platforms must be as- 

 certained; (4) marine bottom deposits must be analyzed accord- 

 ing to the source of the material, and the percentage of the cal- 

 cium carbonate contributed by the different agents estimated; 

 (5) the rate of growth of corals needs to be known, especially 

 for the light it may throw on the rate of reef formation. 



