DJ;PARTMENT OF MARINE BIOLOGY. I33 



On any reef where G. Hahellum occurs in large numbers the conformation 

 of the individuals to a series of sizes is very noticeable. This was very 

 clearly shown when 170 specimens growing upon a single small reef were ar- 

 ranged in series according to their heights. 



After the group of small individuals less than 65 mm. in height, the next 

 large group centered about a height of 220 mm., with less than a dozen speci- 

 mens of intermediate sizes. The absence of an intermediate group, centering 

 about 150 mm., would indicate that very few planulse became attached during 

 the summer of 1910, or, as is more probable, that the very young individuals 

 were unable to withstand the effects of the violent wave-action developed 

 during the hurricane of October 17, 1910. The next, and on this particular 

 reef at least, the largest group centers about a height of 280 mm. Among 

 the specimens over 300 mm., the "steps" were not so well marked, although 

 the largest specimens (600 to 750 mm.) were separated by a considerable in- 

 terval from those of the next smaller size. Among the specimens of P. 

 Hexuosa on this reef there was also a marked absence of individuals which 

 from their size would appear to be two years old. 



REGENERATION EXPERIMENTS. . 



The results of the regeneration experiments recorded in the report for last 

 season* showed the general results from the operations upon a number of 

 specimens of 3 species of gorgonians. In every instance it was found that 

 after another year there had been little change in the specimens under obser- 

 vation. Where the upper portion had been cut from the "leaf blade" of G. 

 Hahellum there is now no evidence of the injury, as the injured "blade" has 

 taken on the usual shape. Those specimens from the blade of which window- 

 like openings had been cut out still show, after two years, the shapes of the 

 pieces removed, and there has been no ingrowth from the periphery of the 

 opening left after the removal of the tissue in the operation. In general there 

 has been only the covering up of the exposed deeper tissues, but no extensive 

 regeneration. 



Where the living tissue was cut from one side of the stem of P. Hexuosa, 

 the polyps which make their appearance on this denuded area do not form a 

 normal calyx, so that when they are retracted the stem appears smooth in- 

 stead of roughened, as in normal specimens. 



The larger branches of Gorgonia acerosa from which the polyp-bearing tis- 

 sues were removed are still covered only by the scar-tissue first formed, in 

 which no new polyps have made their appearance. 



The results of all the regeneration experiments confirm the observations 

 upon the recovery from injuries received naturally, namely, that while inju- 

 ries to the actively growing portions of the colony (smaller branches or 

 edges of blade in G. flabellum), are soon repaired and rendered unrecogniza- 

 ble, the injuries of older portions of the colony are. on the other hand, sim- 

 ply healed over without any restitution of the normal structure. 



BREEDING OF PALYTHOA. 



Having been unable to obtain ripe eggs of Palythoa previous to August 7, 

 when the laboratory was closed for the season of 191 1, arrangements were 

 made to have J\lr. W. L. Wilson, the collector, continue the observations 

 during August and September. These observations showed that the greater 



* Carnegie Institution of Washington Year Book No. 10, pp. 143-145. 



