north of Piney Point. It is unfortunate that the 

 growth rates of the sponges in the area off 

 Cape Sable in the south could not be estab- 

 lished as well, as this would have assisted 

 greatly in understanding the relationship of 

 temperature and sponge growth. 



To obtain the growth curve for wool sponges 

 in figure 7a, the growth data from each tagged 

 sponge was recorded individually on a graph 

 and the mean slope between them taken as the 

 average growth rate of the sponges. The re- 

 sults obtained by compilation of the data in 

 this way agreed well with those obtained by 

 Moore (1910b). The data gathered indicated 

 marked variation of growth between sponges 

 on the same bar. 



AGE IVEAflS AND yONTHS) 



Figure 7a.--Growth rate of wool sponges. The light line 

 is based on observation dsta of the growth of tagged 

 sponges on bars in the upper Gulf. The heavy line is 

 the modified growth curve, dashed portions extrapo- 

 lated. 



AGC IN YEARS 



Figure 7b.- -Volume-diameter relationships in the wool 

 sponges. Solid line based on observed growth rates. 

 Lower dashed line beyond 6-inch diameter based on 

 the growth formula. The upper dashed line of the 

 growth curve represents the more probable growth 

 rate under natural conditions as discussed in the text. 



Moore determined the average yearly in- 

 crease in diameter of wool sponges to be be- 

 tween 1 and 1.2 inches, beginning with a cutting 

 of 10 cubic inches. For a comparable 4-year 

 period the yearly increase of wool sponges 

 growing naturally on the bottom determined 

 by the short-term experiment during the 

 present investigation was 1.25 inches. 



Yearly Growth Factor 



Growth may also be expressed in terms of 

 a growth factor, the number of times a sponge 

 increases in volume during a 1-year period. 

 With Moore's method the growth factors deter- 

 mined for the present experiment from the 

 growth curve were: 



Second year of growth - 3.2 

 Third year of growth - 2.0 

 Fourth year of growth 



1.6 



The average growth factor for this 3-year 

 period was 2.3. Moore obtained a growth factor 

 of 1.9 for cultivated sponges in shallow water 

 at Anclote Key for a comparable period and 

 size of sponge. Crawshay (1939), reviewing 

 experiments with sponge cuttings at Tumeffe, 

 British Honduras, considered a growth factor 

 of 2.0 or more as adequate and 2.5 as good. He 

 also considered a growth factor of 3 or more 

 as high and suggested that the exceptional ac- 

 cumulation of waste matter which could accom- 

 pany the high food intake necessary to maintain 

 this growth factor might be unhealthy for the 

 sponge and result in disease. This could happen 

 with any deterioration of optimum growth 

 conditions. 



With a growth factor of 2.3 during the first 

 few years of the growth of the sponge found in 

 the upper Giilf, a sponge would require about 3 

 years to reach the legal size of 5 inches in 

 diameter from the time of attachment of the 

 sponge larva and almost 4 years before the 

 sponge was 6 inches in size. A listing of vari- 

 ous growth factors obtained during the past and 

 present experiments show wide variation for 

 comparable growth periods: 



Sugar Loaf Key, Florida (Moore, 



1910b) 1.86 



Anclote Key, Florida (Moore, 



1910b) 1.91 



17 



