EEPORT OF THE COMMISSIONER OF FISHERIES. 85 



that lead wire is too weak to support even its own weight in the lengths^ 

 necessitated by the conditions of the experiment, and in the preceding 

 fiscal year the expedient was tried of using ordinary tarred marline 

 with a thin casing of lead. The marline supplies the required tensile 

 strength, and the lead, besides serving as a protecting covering for the 

 cordage, furnishes the desired surface for the attachment of the 

 sponges. The cuttings within a week attach themselves to the lead 

 and soon form an adhesion sufficiently close to prevent oscillation in 

 the waves and yet not so close as to offer an impediment to their 

 removal from the wire when it is desired to harvest them. Lead- 

 covered marline had been in use for twenty months at the close of the 

 fiscal year, and yet showed no indications of impairment in strength. 

 It must last twice that long, however, to demonstrate its usefulness. 



When leaded marline was first employed the lines were rigidly 

 attached to the stakes, but the continual swaj^ ing in the waves caused 

 repeated flexure near the point of attachment, and resulted in fractur- 

 ing the inductile lead and abrading the marline core to the breaking 

 point. A flexible attachment is now employed, and there is no longer 

 this difficulty. 



Asbestos cord, treated with a mixture of paraffin and asphaltum and 

 incased in lead, and lead-covered underwriters' wire have also been 

 tried, with results in general similar to those above described. 



With the use of lead it became necessar3'^ to abandon aluminum wire 

 for attaching the sponges and closing the slit, as electrolytic action 

 destroyed it before it could serve its purpose. Rubber bands are now 

 emploA^ed instead, care being exercised to have them of such length, 

 compared to the size of the cutting, that no undue pressure is exerted 

 on the tissues of the sponge. 



The growth of the sponges during the year has been satisfactory, 

 sorfie of them having attained a size of over 5 inches at the age of 

 thirty months. Others, eighteen months old, are 4 to 4^ inches in 

 diameter. At Anclote Key there has been a somewhat alarming 

 mortality among the larger ones, and this may indicate the beginning 

 of serious difficulties, as there is a possibility that these sponges may 

 be approaching their limit of growth, if such exists. At Sugar Loaf 

 Key and in Biscayne Bay, where the growth has been slower, this 

 difficulty has not developed. During the next fiscal year, this matter 

 will receive special attention, as the experiments are now approaching 

 a critical stage. No apprehension is felt that insuperable difficulties 

 will be encountered. 



THE BLUE CRAB. 



The investigations and study of the life history of the blue crab in 

 Chesapeake Bay begun by Prof. W. P. Hay in 1902 have been contin- 

 ued by him during the past fiscal year when opportunity offered. 

 Many important observations were made at Crisfield, Md., and at 



