volume of the sponge remains a constant in 

 relation to the surface area. 



If the size of the sponge were periodically 

 reduced by dividing it into cuttings, it may be 

 that the original sponge material could be 

 kept living indefinitely, assuming favorable 

 growth conditions. This has been done in part 

 in the Bahamas' sponge plantation where 

 sponges have been cut several times from the 

 same base. Some of the bases are close to 

 16 years of age and are repeatedly developing 

 new upper growths. 



Several individual sponges of noncommercial 

 varieties have been observed by me for over 

 15 years. These sponges had reached 3 feet 

 in diameter when first seen. This may be the 

 maximum size obtainable under the local con- 

 ditions present, for after a winter when tem- 

 peratures were unusually cool a decline in 

 size was noted. Similar reductions in size of 

 sponges growing in aquaria were observed 

 when water temperatures dropped suddenly. 

 This reduction in size seems to be related 

 only to temperature changes. 



An examination of the ecological conditions 

 existing in each area indicates that food supply, 

 temperature, and water currents are the pri- 

 mary factors affecting the growth rate. The 

 effect of these factors on growth will be dis- 

 cussed in the section on ecology. 



Healing and Growth of Cut Surfaces 



Part of the field study on growth was ex- 

 perimentation on regrowth of the sponge from 

 the cut base to show the possible value of 

 cutting the sponge from the base rather than 

 using a hook to remove the sponge. Weekly 

 observations were made of the cuttings of wool 

 and yellow sponges attached to cement bricks 

 In aquaria with running salt water. Most 

 closely related to the field experiments were 

 the observations made on the healing of the 

 cut surfaces and the external evidence of re- 

 organization in the canal system of the sponge 

 cuttings. 



Initial healing and sealing off of the cut sur- 

 faces took place within a few hours after 

 cutting. After 3 days, primary healing of the 



cut surface had occurred and a new outside 

 surface layer laid down. At the end of 2 weeks 

 the cut surfaces had become black in color, 

 and within the month the exposed internal canals 

 had filled in. A number of small volcanolike 

 oscules had also developed, from which a 

 noticeable current of water passed. 



The bases of the sponges in the field study 

 were examined about 3 months after the top of 

 the sponges had been removed by cutting. The 

 appearance of the regrowth from the cut base 

 was essentially that of a number of small 

 coalescing sponges. These bases had retained 

 their original mass and had developed a number 

 of prominent oscules about one-half inch in 

 height scattered over the cut surface. Because 

 of its relatively thin layer of living material 

 on the rock, the sponge had not had sufficient 

 food reserve to fill in all the larger exposed 

 canals and only a dermal layer had been laid 

 down. Beyond the formation of the oscules no 

 real growth had been made in this relatively 

 short period of time. 



CULTIVATION OF SPONGES 



Aristotle in 350 B.C. noted the regrowth of 

 sponges from torn bases. There are records 

 of experiments of sponge cultivation during the 

 18th century in the Mediterranean Sea, and 

 many experiments have been carried out since 

 that time in various Mediterranean countries, 

 British Honduras, the Bahamas, and Florida. 



From the time that sponging became an im- 

 portant industry in Florida, the harvesting 

 methods have been deplored as destructive 

 and sponge cultivation has been suggested as a 

 remedy to assure an adequate continuing har- 

 vest. The most extensive cultivation experi- 

 ments attempted were by Moore (1910b). In 

 the several cultivation experiments tried in 

 Florida, the sponges were grown on metal 

 spikes, wire, and cane, with cement triangles 

 or discs used as the bases for attachment. 

 All the experiments eventually ended because 

 the sponges were destroyed either by storms 

 or by the spongers, some of whom were 

 opposed to the experiments. Principal source 

 of failure was the poor locality chosen for the 

 experiments. 



19 



