196 PKOJECTS FOR THE IMPROVEMENT OF SPONGE-FISHERIES. 



opened. Until growth has repaired these injuries, the cut fragment 

 must necessarily be at a disadvantage, as compared with a complete 

 sponge of its own size,* and I am of opinion that the complete small 

 individual is at a disadvantage as compared with the equal portion of a 

 large and powerful sponge. 



We have no knowledge of any causes to check the growth of a 

 sponge, though it may be assumed (without positive proof) that they 

 are subject to senile decay. But we have no knowledge that the tissues 

 of a senile sponge undergo rejuvenescence when they are divided 

 into fragments ; and the observations of Buccich — that certain cuttings 

 never grew at all, and that the growth was unequal — indicate slightly 

 the more probable hypothesis that the fragment of an effete sponge 

 is itself effete. 



It is urged that misshapen sponges may thus be utilized. But 

 it must be pointed out that misshapen sponges can still breed, and that 

 there is no evidence how far the reproductive function is interfered 

 with by the cutting process ; I should myself expect such interference 

 to be important. Buccich found 90 per cent, of his cuttings attain 

 " marketable size " in seven years. Whether this is advantageous 

 depends on the length of time taken by a self-sown sponge to attain 

 " marketable size." If this be seven years also, then the method 

 is profitable for misformed sponges ; if it be only one year, then 

 the quantity produced by natural reproduction would be greater than 

 by the method of cuttings. 



I know of no observations which favour the former hypothesis ; 

 and some siliceous sponges have been observed to grow to an equal 

 size in a single season. 



In view of the commercial importance of this question, it appears 

 highly desirable that observations should be made as to the rate of 

 growth of self-sown sponges. Until such are made, I cannot see that 

 we have any reason to suppose that propagation by cuttings is in itself 

 likely to increase the value of a sponge field. 



(2) The above conclusion coincides nearly with that of Dr. 

 von Marenzeller, in 1878. But the second question appears to have 

 escaped his notice. 



Briefly, I consider that the method of Buccich may possibly be made 

 useful as a means of inducing sponges to grow on a more extended 

 surface tlian the sea-bottom, and under more advantageous condi- 

 tions. 



It has been recognised among certain littoral sponges that gigantic 

 specimens are generally found hanging from the under surface of 



* In the Florida exiioriuieuts it is recorded that this was the case. 



