The process of fertilization of the 

 ova within the wool sponge suggests 

 that for almost every sperm taken in, 

 one egg will be fertilized and mature 

 to the larval stage. The number of em- 

 bryos produced, therefore, will be in 

 direct ratio to the number of sperm 

 entering the sponge. Further, the num- 

 ber of spermatozoa being taken in will 

 be in direct relationship to the con- 

 centration of sperm in the water sur- 

 rounding the egg-producing sponge. 



2. Sponges possibly can reach a size and 

 shape that inhibits the production of 

 eggs and larvae . — Sponge fishermen 

 have observed that when they formerly 

 found densely populated beds of very 

 old doughnut- shaped sponges there 

 were few if any young sponges develop- 

 ing. Doughnut- shaped sponges were ob- 

 viously past their optimum size of 

 development. Extensive fishing of these 

 beds resulted in the appearance of large 

 numbers of small sponges the follow- 

 ing year. (Regrowth of pieces of sponge 

 left on the bottom when the large 

 sponges are torn free could account for 

 the small sponges.) The possibility is 

 suggested that when a wool sponge 

 reaches a 12-inch size and begins to 

 form into a ring, it may be in a period 

 of senescence. (See section on growth 

 for a discussion of this phenomenon.) 

 At this point the food intake may be 

 below the demands of the living tissue, 

 and there may not be sufficient food 

 reserves for the larvae to become vig- 

 orous enough to leave the sponge. If 

 they do leave they may not be strong 

 enough to attach and metamorphose 

 into young sponges. 



Since small pieces of even the largest 

 sponges can be used successfully in 

 cultivation and these grow into vigorous 

 young sponges, the argument cannot be 

 used that the tissues of the large 

 doughnut- shaped sponges become too 

 old to produce ova. 



3. Wool sponges may not be capable of 

 self-fertilization.— If sponges were 



able to self-fertilize, the sponges found 

 in areas of low sponge concentration 

 would have as many larvae as those in 

 areas of high sponge concentration. At 

 many stations in area D (see appendix) 

 where only few sponges were encoun- 

 tered, none contained developing 

 larvae. 



4. Sponges less than 5-1/2 inches in 

 diameter may not be the sperm-pro - 

 ducing sponges . — The presence of 

 large numbers of sponges of less than 

 5-1/2 inches in diameter had no rela- 

 tionship to the percentage of mature 

 sponges that were producing larvae. 

 For example, on one bar, Station 

 XXVlll (table 2), the concentration for 

 all sponges was 20 per acre but only 2 

 per acre for sponges of mature size. 

 The mature sponges here had very low 

 egg counts. 



5. From the evidence gathered there 

 is an indication that only 1 out of every 

 200,000 or more larvae actually settles 

 on the bottom and grows to maturity. — 

 On five bars, in less than 24 feet of 

 water where intensive work on the 

 ecology and growth of the sponges was 

 carried out, of the 108 sponges meas- 

 ured, the ratio of mature sponges to 

 sponges of less than 5-1/2 inches in 

 diameter, was 1: 3.6. A number of the 

 sponges were obviously regrowths 

 from old torn bases. I assume that the 

 number of mature sponges present was 

 barely enough to maintain the concen- 

 tration of sponges at the level observed. 

 Since the average mature wool sponge 

 in the area was little more than 6 

 inches in diameter and sponges of this 

 size produce an estimated 200,000 or 

 so larvae per year, it would appear that 

 this level of egg production in this area 

 is the minimum production per mature 

 sponge required for maintenance of the 

 population. Almost all of the sponges 

 over 6 inches in diameter were being 

 harvested each year in the area. It may 

 be suggested that if the average diam- 

 eter of the mature sponges in an area 

 Is only 6 inches and all sponges over 



11 



