DesmidiecE.'] infusoeial animalcules. 271 



to the typical D. furcigerus, yet they agree better with the verbal 

 characters of the genus than with those of any other known to 

 Dr. Bailey ; therefore, he refers them here pro\'isionally. 



Genus Tetmemokus (Ralfs.)— Frond simple, elongated, straight, 

 cylindi-ical, or fusiform, slightly constricted at the middle ; segments 

 emarginate at the end, but otherwise quite entire. The frond is 

 elongated, as in Penium, but differs in its emarginate ends; the 

 same character and the elongated frond separates it fi'om Cosmarmm. 

 From Eiiastrum, with which it agrees in the emarginate extremities, 

 it differs in being cylintbical or nearly so, and in the segments beuig 

 neither lobcd nor siiiuated ; the fronds are also free fr-om inflated 

 protuberances. 



T. Bnhissonii. — In front view with parallel sides, but in lateral 

 one fusiform ; ends without any projecting processes ; pimcta in 

 longitudinal lines (P. 13. f, 12, 13.) 



Var. (J.) turgidus. — Larger; constriction greater ; segments some- 

 what inflated. Frond four to six times longer than broad. The endo- 

 chrome is dark green ; its large vesicles in a single central row. 



T. IcBvis. — Somewhat tapering in front view; ends truncate; 

 lateral view fusiform ; puncta none or very indistinct ; four to six 

 times longer than broad, constricted at the middle. Length 1-3 74th. 



The process of fo]-ming the sporangium is interesting, as it exhibits 

 a striking similarity to the change during the formation of similar 

 bodies in Staurocar2)us among the ConjugattB. In Staurocarpus, after 

 conjugation, a subquadi-ate cell is formed, within which the endo- 

 chrome is collected. The latter is at first of the same figure as the 

 cell, but in at least one species, is at length condensed into a compact 

 globidar body, and in every species the cell >vdth the contained 

 sporangium, finally separates fi'om the filaments with which it is 

 connected. In this separate state I can discover no character by 

 which to distinguish the sporangium of Tetmemorus from one be- 

 longing to a species of Staurocarpus. Length. 



T. granulatus. — Fusiform both in the front and lateral views, and 

 ending in a colouiiess projecting lip-like process ; about six times 

 longer than broad ; very slightly constricted. Empty frond with 

 scattered puncta ; near the central constriction they form one or two 

 tranverse lines in each segment. 



