PROJECTS FOR THE IMPROVEMENT OF SPONGE-FISHERIES. 197 



a rock, or floating body. * This has been observed for calcareous 

 sponges on the floating frameworks set for oyster-spat in Holland 

 (9), on the bottoms of ships in Naples harbour (9), on the under surface 

 of a buoy at the Isle of Man (13), and may be verified to some extent 

 even on the shore-rocks near the Plymouth Laboratory. 



I am aware of no direct observations on this point with regard to any 

 greater depth. But the same advantage, probably, there also attends an 

 elevated position. Thus, Hyatt (5) says that " The sponges near Nassau 

 lie ... . always in currents, sometimes running three or four miles an 



hour Both of these conditions are essential to sponge growth, 



namely, a continuous renewal of aerated water, and a plentiful supply of 

 food." And Eathbun (11) says of cuttings in Florida: "One was 

 placed in a cave or bight, where there was little or no current, and its 

 increase in size was very slight. The other specimens were placed 

 in tide -ways, and have grown from four to six times their former 

 bulk." 



Now, where a current of water is flowing over a solid surface, a very 

 slisht increase in height from the surface means great increase in 

 velocity of current. Buccich's method placed the cuttings from four to 

 twelve inches above the sea bottom, and with their centres four inches 

 apart, disposed on four parallel gratings separated from each other by 

 the same distance. He appears to have dealt only with the small, fine, 

 toilet sponge (7) ; but even so, I think the system capable of improve- 

 ment. I consider great advantage might be obtained by inducing 

 sponges to grow on hurdles rising some feet above the sea-bottom, and 

 allowing a distance between the centres of four inches for cuttings, and 

 twelve inches or more for grown sponges, with a distance between every 

 two hurdles equal to their own height. I should experiment by ballast- 

 ing and sinking a hurdle such as is used for a deer fence, preferably of 

 enamelled iron ; with (a) canes tied across it parallel to the bars, and 

 (h) vertical tiles, hung in pairs on the bars. To these cuttings, or small 

 sponges, might be attached ; and I should try making the attachment 

 with a needle and thread, using the method of Buccich as a control 

 experiment. The cuttings on the canes would grow round them to 

 form perforated spheres. These Marenzeller states to be of less value 

 in the market, owing to the perforation, but I should imagine they 

 would soon acquire a value of their own, as they would have no torn 

 surface. These, also, as being exposed on all sides, would probably 

 grow most rapidly. The cuttings on the tiles should become of the 

 ordinary hemispherical type. It might be found that young sponges 



* Cf., especially Vosmaer (9), where he points out the advantages to the sponge of 

 a position where water flows freely round it. This was to some extent recognised, long ago 

 by Grant ^/c Johnston (1). 



