b TRANSACTIONS OF THE WAGNER FREE 



feature being an unusual abundance of genimules — a fact particularly notice- 

 able in those from the mangrove roots. A more minute examination shows 

 that the gemmules of the latter are roughened, while the surfaces of those 

 from the grass-stems are singularly smooth, and that this difference is 

 caused by the unequal lengths of the gemmule birotulates in the one case 

 and their uniformity in the other. Their average length is rather less in 

 the latter sponge, but this is almost the only difference between them. 

 Both forms remind the observer of Mcyenia subdivisa from the St. John's 

 River, Florida, in the general character of the gemmule spicules and in the 

 subdivision of their spines, but neither equals the typical forms of that 

 species in the robustness of its parts. The shafts of the birotulates of both 

 are, however, much longer than those of the ordinary type of M. fluviatilis. 

 On the whole, I cannot satisfy myself that either can properly claim specific 

 distinction, and I incline, for the present, to consider them only as connect- 

 ing links among.st the many flluviatiloid forms. 



Another package received from Mr. Willcox contained fresh-water 

 .sponges, many of which incrusted such well-known marine organisms as 

 barnacles and the calcareous tubes of Serpul<2. He writes : " The sponges 

 adhering to the barnacles were found on the rocky bottom of a rapidly 

 flowing creek four or five feet deep, about twelve to fifteen miles east of 

 Lostman's Key, which is twenty-five miles north of Cape Sable, on the 

 southwest coast of Florida. The presence of the barnacles can only be 

 accounted for by the action of the strong southwest winds which some- 

 times back up the salt water into the rivers and creeks. The young bar- 

 nacles, having followed the influx of salt water and attached themselves to 

 the rocks on the bottom, may have attained a portion of their growth 

 while immersed in fresh water, after the subsidence of the salt water." 

 He names Dr. Leidy as supporting the probability of this theory, and also 

 as stating that their early growth must be relatively rapid, from the size 

 they are known to have attained upon such perishable supports as apples 

 and cranberries. 



A few of the sponges collected at this place are Meyenias and do not 

 .seem to differ from those just mentioned ; the greater number, however, 

 belong to the genus Spongilla and are clearly allied to the cosmopolitan 

 6'. lacustris. Two points alone seem to warrant me in honoring it, at least 

 provisionally, with the name of the noble in.stitution of which Mr. Willcox 

 is an active manager. These are the abnormal local conditions just men- 

 tioned and the unprecedented multitudes of its dermal .spicules. 



Anticipating the technical description given below, I would call atten- 

 tion to the unusually white color of these sponges when dry, and to the 

 appearance of a compact incrustation resulting from the massing upon the 

 surface of the dermal spicules just alluded to ; to the singular habit of hiding 

 away their gemmules within the barnacles or amongst the convoluted .stems 



