144 



REPORTS ON INVE^STIGATIONS AND PROJECTS. 



On the same area of reef the location of 2;^ dead colonies could be deter- 

 mined. With three exceptions, all of these skeletons were covered by a 

 growth of living MilUpora alcicornis. When a colony had been only a short 

 time dead the MilUpora conformed to the shape of the original gorgonian 

 colony, even showing the meshwork of the skeleton of G. Hahellum. In other 

 instances the presence of the gorgonian skeleton within the MilUpora colony 

 could be demonstrated only after some of the projections on the latter colony 

 had been broken off, when it would be found to contain a piece of gorgonian 

 skeleton as a central axis. 



The percentages of specimens of each different size, as shown in the table, 

 when considered in relation to the rate of growth, seems to indicate that the 

 norm of size for some species is reached within a comparatively few seasons. 

 Gorgonia acerosa, on the other hand, would seem to have a more regular 

 increase in size with a longer growing-period than the other species listed, as 

 seen by comparing the figures in the fifth group of the last table. The com- 

 paratively small number of skeletons of dead colonies found on the reef 

 indicates that the death-rate is very low. The fact that the skeletons, espe- 

 cially when covered by MilUpora, will persist for a number of years in a 

 recognizable condition makes it appear certain that the life of a gorgonian 

 colony must extend for a considerable period after the norm of size has been 

 reached. 



REGENERATION EXPERIMENTS. 



In the course of my work during the summer of 19 lo it was observed that 

 many colonies of the different species of gorgonians had undergone injuries 

 of greater or less extent, and in order to determine the capacity for and rate 

 of regulatory growth the following experiments were undertaken : 



The species used for most of the experiments were those for which the 

 greater number of measurements had been made — Gorgonia Hahcllum, G. 

 acerosa, and Plexanra Hexuosa. All of the operations were extensive, in- 

 volving the coenenchyme. and frequently the skeleton as well as the polyps. 



The following table shows the nature of the operation and the general 

 results for a few of the experiments : 



Pieces of the regenerating branches of Gorgonia acerosa were preserved 

 when the reef was visited in January 191 1 and sections were cut and studied. 



