760 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [6] 



of an inch in diameter, and hence of a sufficient size to be preyed upon 

 by a larger arthropod. The remarkable Fyrocystis noctihica, discovered 

 by Mr. Murray, and nearly a millimeter in diameter, is another inter- 

 esting surface form, as is also the P. fusiformis, which is allied to it. 

 Both are x)hosphoresceut surface swimmers, and fall within the reach of 

 other surface animals as a probable source of food. To these may be 

 added the curious group of the Challengerida, together with the whole 

 of the Eadiolaria, with their siliceous shells, which, in the warmer parts, 

 of the high seas, actually tinge the surface when some of the highly- 

 colored forms are abundant. From the surface of the mid-Atlantic the 

 Challenger crew obtained stalked iufusorians fixed to the shell of Spi- 

 rula ; also an abundance of large radiolariaus. Haeckel, Monograph of 

 the Radiolaria, says the largest living Eadiolaria measure only a few 

 lines in diameter, but most of them are much smaller, and attain 

 scarcely a tenth down to a twentieth of a line in diameter. At Saint 

 Jerome's Creek, Maryland, in one of its arms which is now used as an 

 oyster park, the writer found an abundance of a fresh-water Heliozoan, 

 not specificially distinguishable from Actinophrys sol. They were found 

 in great abundance at times on the surface of the slate collectors which 

 had been put down for the purpose of enabling the free-swimming fry 

 of the oyster to fix itself. This raises the question whether the fresh- 

 water protozoan fauna does not overlap the marine. The water in the 

 situation mentioned was not simply brackish, but positively salt. In the 

 same place great numbers of stalked and tube or test building ciliate 

 forms of Protozoa were also found. The magnificent bottle-green Freia 

 producta was found in the same locality in the greatest profusion. Some- 

 times several hundred mighthavebeen counted on a single square inch of 

 the surface of oyster shells, slates, or boards, giving such surfaces a dark- 

 greenish or speckled tint from their numbers. Very small species of 

 nudibranchiate mollusks {JEoUs and Doris) were found creeping amongst 

 and over the forest of Protozoa, pasturing oft" of them. Amongst the 

 tubes of the Freia, and attached to them, a small operculate Gothurniay 

 with a rich brown-colored test, was found in abundance, and, rarely, a 

 very curious form of Tintinnus, with a tubular, subulate test, to the 

 inside of which the stalk of the inhabitant was attached, at one side^ 

 about half way up from its base. The open or mouth end of the per- 

 fectly hyaline test was very strongly toothed, or serrate. The species 

 may be named Tintinnns Fergusonii. Another species of Freia has been 

 detected on the coast of New Jersey, by Professor Leidy, and, from a 

 verbal description given me by Dr. H. C. Evarts, a species occurs in the 

 vicinity of Beaufort, N. 0. So abundant was Freia producta in Saint 

 Jerome's Creek that I apprehend that in its free-swimming young state, 

 previous to the time that it commenced to build its test, it afforded not 

 an inconsiderable proportion of food to the oysters planted in some 

 parts of those waters. Besides the Freia there were innumerable indi. 

 viduals of Vorticella observed. One of these had a very thick brown- 



