22 REPORT OF THE COMMISSIONER OF FISHERIES. 



growth of undesirable unicellular and filamentous alga?, which give to 

 the oyster a disagreeable muddy flavor. The use of copper sulphate 

 for the destruction of such algas has giv T en satisfactory results. 



Oyster and clam experiments in North Carolina. — The oyster-grow- 

 ing experiments in North Carolina conducted in connection with the 

 Beaufort laboratory have been continued. The increasing importance 

 of the quahog, or hard clam ( Venus mrrcenaria), in North Carolina, 

 owing to the development of the canning industry, has suggested an 

 inquiry into the habits, growth, and propagation of this species, and 

 in connection with the oyster work experiments in the planting and 

 cultivation of this valuable mollusk have been undertaken. 



EXPERIMENTS IN SPONGE CULTURE. 



The experiments in the raising of sponges from cuttings at several 

 points on the coast of Florida have been continued, and the results of 

 the year's operations show conclusively that it is possible to raise 

 sponges of merchantable size in this manner, a number of specimens 

 6 inches in diameter having developed from plants made three years 

 before. The sponges artificially grown are of excellent shape and 

 quality, and are superior in both of these respects to sponges growing 

 naturally in the same localities. The economic aspects of the experi- 

 ments, however, are still to be demonstrated, as the search for a suit- 

 able material for support of the cuttings until they reach commercial 

 maturity is yet unrewarded. Bricks, rocks, and similar bodies on the 

 bottom will undoubtedly serve, but this method, besides having cer- 

 tain mechanical drawbacks, produces sponges inferior in shape and 

 texture to those grown suspended above the bottom. They more 

 nearly resemble the natural sponges, especially in the possession of a 

 ''root," which is the raw surface resulting from detachment from the 

 support; it is the "root" that first wears out in use, and the durabil- 

 ity of this part determines the wearing qualities of the sponge as a 

 whole. Sponges grown artificially on wires raised above the bottom 

 have a surface uniformly felted and with corresponding uniform 

 wearing qualities. 



During May, 1905, there was a considerable mortalit}^ among the 

 sponges planted at Anclote Key, affecting principally those in shoal 

 water and near the surface. It seems probable that the condition was 

 due to the prevalence of hot weather with heavy showers, coincident 

 with exceedingly low tides. The extreme sensitiveness of sponges to 

 the influence of rain water has before been noted. 



EXPERIMENTAL CULTURE OF DIAMOND-BACK TERRAPIN. 



During the summer of 1904 the investigation of the diamond-back 

 terrapin was continued at an experimental pound on the eastern shore 



