Ndviculacea.'] infusorial .VNiMALorLES. S77 



Melostra. aurichdcea {Yiyitz,) — Filaments more slender, and more 

 uniform in size ; joints larger, and more closely united : it especially . 

 differs in having two central lines, and striated junction-surfeces, 

 and in not turning green in drjing. 



Niigeli describes and figures a species wliicli he refers to the genus 

 GaUionella ; but it is a doubtful member. His description, however, 

 especially that of the self-division, induces us to give it nearly in his 

 own words, with his name, (Ray Society, 1848, p. 219.) 



GaUionella (?) (Nageli.) — Eigure shortly cylindrical. Diameter 

 .014th to .027th of a line. 



Both the terminal surfaces of the cylinder are flattened, so that, 

 when seen sideways, it appears rectangular, with the angles rounded 

 off. It is composed of one simple cell, whose membrane is covered 

 by a siliceous plate, and its cavity contains chlorophyll granules, which 

 lie upon the membrane in two circular bands. (P. 24, f. 26 to 28.) 

 Each of these bands occupies one of the two obtuse angles of the 

 cylinder, and appears annular from above rectilinear, from the side 

 .(See description of Plate 24.) 



In developing, the relative length of the cylinder increasing, a 

 septima divides it into halves, (P. 24, f. 28c) which, when com- 

 plete, the latter separate as t\^h distinct beings. The nascent 

 chlorophyll-granules are either spread equally over the surface, or 

 more frequently arranged in radii from the nucleus in the centre ; 

 they lie in the course of the currents streaming from the nucleus. 

 Compared with a cell of Conferva, or of Spirogyra, all three agree in 

 the forming of a septum, in the similarity of their contents, and in 

 the depositions of extra-cellular substance. But GaUionella differs 

 from both, by the production of an individual from every ceU ; also, 

 by the chlorophyll forming two lateral bands, and the siliceous 

 extra-ceUular substance an intermediate one. 



" So far as my investigations go, GaUionella, which, according to 

 Ehrenberg, posseses a bivalved or multivalved shield, agrees with the 

 above-described plant in all essential particulars. The lines, for 

 instance, which would intimate a division of the sheU into two or 

 more pieces, are the septa by which the cell-division is effected. As 

 in the filiform Algoe, these walls at first appear as delicate lines ; 

 then, by an increase of thickness, seem two clearly defined lines, and 



c c 



