82 Papers from the Marine Biological Laboratory at Tortugas. 



The most complete records of the growth of specimens of G. flahellum 

 and P. flexuosa among my data are those for some specimens growing upon 

 a single coral head {Orbicella annularis) some 12 feet in diameter, situated 

 about 200 yards west from the laboratory upon a shallow reef. Table i 

 shows the growth-record for the period since June 1910, and gives the 

 original size and the change in height of the same specimens of gorgonians 

 after 7 months, i year, and 2 years from the time of first measurement; with 

 the percentage of increase in height for the 2 years. 



Similar records of individuals of the same species growing upon tiles, 

 photographs of which constitute a part of this report, are shown in table 2. 



Table 2. — Heights of gorgonians attached to tiles to show groivth in a year. 



Tile and species. 



July 191 1. Aug. 191 2. 



Per cent 

 increase. 



mm. mm. | 



T-i» r / G. flabellum 6S 148 [ 127.69 



^"^ M P. flexuosa 130 iSO ! 15-38 



T-i^ o 1 P- flexuosa (a) / I45 I7S i 20.62 



lile 2 1 p_ flexuosa (6) , 70 1 120 70.43 



Tile 3. G. flabellum 41 124 202.43 



All of the specimens recorded in table 2 were selected without any 

 special reference to size, as at that time no data were at hand to afford the 

 basis for a correlation between size and age. Small (young) individuals 

 of either of the above-listed species were so rarely found on the reefs during 

 the period of observation in June 1910 or July 1912 that, although the 

 specimens on any of the reefs studied could be readily arranged into a 

 series of groups, each containing individuals of about the same size, the 

 relation in respect to age among the several groups could not be determined 

 with certainty. 



The study of the same areas of reef in August 1912 showed the presence 

 of a considerable number of small specimens of both species. On the coral 

 head west of the laboratory there was found on August 21, 1912, seven 

 specimens of P. flexuosa, which had become attached, or at least had become 

 noticeable, since July 23, 191 1. The length of these specimens, in order of 

 magnitude, was 25 mm., 26 mm., 31 mm., 32 mm., 42 mm., 42 mm., and 

 46 mm., respectively. Beside these there was found a single young specimen 

 3 mm. in length, which consisted of only two calyces and polyps. The 

 identification of this specimen as P. flexuosa, which is based upon the 

 character of the spicules and that of the orifice of the calyx, is at best 

 uncertain. The specific identity of the specimen is of considerable interest 

 in connection with other data bearing on the time and duration of the 

 breeding season, as will be pointed out in the section of this paper dealing 

 with oecology. 



On a shallow reef east of Loggerhead Key, where measurements of all 

 gorgonians had been made yearly since 1910, there were found 15 specimens 

 of P. flexuosa less than 50 mm. in length. These were not of a recognizable 



