Sketch of the Infusoria of the family Bacillaria. 327 



confervoid, resulting from perfect divisioti of the carapace, and 

 imperfect division of the mantle. 



In this genus, corpuscles which cannot be distinguished from 

 those of Navicula are assembled together in vast numbers, in flex- 

 ible membranous tubes, within which they may often be seen to 

 move freely. They doubtless often leave these tubes, and then 

 appear like species of Navicula. 



I have noticed several American species, but I am unable to 

 decide whether they are identical with any hitherto described, 

 as I have had very little opportunity to study our species in a 

 living state and have no foreign specimens or figures to compare 

 them with. I shall therefore content myself with merely giving 

 the forms of the frustules found in each species, and such addi- 

 tional particulars as seem most interesting. 



1. Naunema . (PI. 3, fig. 14.) The figure represents cor- 

 puscles from a branching species found on the shores of Staten Island, 

 N. Y, The tubes are whitish, containing long rows of corpuscles, 

 strung end to end, each of which contains two round globules looking 

 like air-bubbles. No trace of strise. 



2. Naunema . (PI. 3, fig. 15.) This figure shows the form 



of corpuscles which filled short robust unbranched filaments, which 

 were exceedingly lubricous. Bunches of filaments about half an inch 

 in length, were found in great abundance on Zostera, &c. at Stoning- 

 ton. Conn. 



3. Naunema . (PI. 3, fig. 16.) This figure shows the out- 

 line of dried corpuscles from a specimen obtained at Stonington, Conn., 

 where it is very common. Its filaments are branched and form larger 

 and longer bunches than the preceding, with which it occurs. 



4. Naunema . (PL 3, fig. 17.) This is from specimens found 



in immense quantities in the Hudson River, at West Point. The masses 

 have not the green color of the two preceding species, but present a 

 rich brown color. The frustules are in all respects like those of Navi- 

 cula, and I have often seen them move spontaneously in their tubes, 

 some going one way and others another. 



In PI. 3, fig. 17, a, is shown the outline of much longer frus- 

 tules, found in tubes similar to those just mentioned. 



Gloeonema. 



Envelope double, carapace siliceous, mantle tubular, tubes sim- 

 ple, often branched, corpuscles curved, resembling Cocconema in 

 a tube. 



