Observations upon the Growth-rate and Oecology of Gorgonians. 83 



size, if present, when the measurements were made over the same area in 

 July 191 1. 



Upon the last-mentioned reef 26 specimens of G. flahellum, less than 65 

 mm. in height, were also found, which were not recognizable when the 

 measurements were made in July 191 1. 



On the basis of these observations, in conjunction with the records given 

 in tables i and 2, it becomes possible to make the records complete for at 

 least two years in the case of G. flahellum (fig. 8, plate 2). Observations 

 after another year's growth will, moreover, fill in the stages to complete the 

 record for six years. 



All specimens of G. flahellum and of P. flexuosa, on a reef east of Logger- 

 head Key, were measured in July 191 1 and again in August 1912. Most of 

 the individuals, as already mentioned, fall into natural "size groups," which 

 for convenience have been designated as follows: Group i, o to 75 mm.; 

 group 2, 75 to 150 mm. ; group 3, 150 to 300 mm. ; group 4, 300 to 450 mm. ; 

 group 5, 450 to 600 mm.; group 6, 600 + mm. As shown in table 3, the 

 percentage of individuals in groups i and 2 varied markedly in the two 

 seasons, while the number of the larger specimens was proportionately 

 similar for the two years. 



Table 3. — Size groupings as shown by measurements of all individuals on a single shalloiv reef. 



The observations upon the breeding season and the attachment of the 

 planulae are intimately connected with those in relation to the absence of 

 small (young) specimens of gorgonians during the seasons of 1910 and 191 1. 

 In June 1910 almost every colony of P. flexuosa examined was carrying 

 mature eggs which could be stimulated to development by the use of chemi- 

 cals which are ordinarily efficacious in bringing about artificial partheno- 

 genesis. None of the planulae among those to be obtained in the tow net 

 could with certainty be identified as those of this species, nor could any of 

 the colonies be kept long enough in aquaria to secure planulae. The evi- 

 dence from artificial parthenogenesis is, however, enough to establish the 

 fact that the breeding season was in progress at that time. 



In July 191 1 some of the colonies of P. flexuosa contained ripe eggs, but 

 the greater number were without apparent gonads. Late in August 191 2 

 not a single specimen was found in which gonads were recognizable, although 

 more individuals were examined to determine this point than in either of 

 the other years. The breeding-season for P. flexuosa is, then, apparently 

 at its height in June. The number of individuals with ripe sexual products 

 diminishes rapidly through July, while by the latter part of August the 



