28 DUBLIN NATURAL HISTORY SOCIETY. 



been described under the title of the ' swarming of the granules,' from 

 the extraordinary resemblance which the mass of moving particles beasr 

 to a swarm of bees. The subsequent history of their development, 

 however, has not been fully traced out ; and this is a point to which 

 the attention of microscopists should be specially directed." With great 

 diffidence I venture to suggest that the statements in the foregoing pas- 

 sage must be based on the swarming movement of the minute granules 

 which I have endeavoured to describe above. I am disposed to believe 

 that the granules which the author terms gonidia are not ciliated ; and 

 although the species of Cosmarium often show the movement, it is by 

 no means confined to that genus, but may be frequently seen also in 

 multitudes of other species. The author then goes on to describe the 

 formation of undoubted zoospores in Pediastrum. As to " resting 

 spores," I imagine he must allude to such bodies as are figured byRalfs 

 in Desmidium Swartzii (Br. Des., tab. iv. f.), where they are not pro- 

 duced by conjugation, but seem to be due to the consolidation of the 

 contents of each individual joint, which becomes enclosed in its own spe- 

 cial envelope, as sometimes takes place in Spirogyra, &c. Braun suggests 

 that the filament met with by Ralfs may have been one which had entered 

 into conjugation with another filament, and that the string of empty 

 cells had been torn away ; but this is certainly not the case, for I have 

 myself met with the species in question in some abundance in precisely 

 the same condition as that figured by Ralfs, and which consists in the 

 cell-contents of a greater or less number in immediate succession of the 

 cells of certain filaments becoming retracted to the centre of the cavity 

 of each cell, and becoming there massed together into a definitely- 

 bounded spore-like body, without any process of conjugation or union 

 of the contents of distinct cells. But I was not able to see any further 

 development, and the specimens soon died. {Vide also, for resting- 

 spores (?) "Micrographic Dictionary," pi. vi. fig. 3 B; also Proc. JSTat. 

 Hist. Soc, Dub., 1858-9, pi. i. fig. 14 — irrespective, of course, of the 

 external abnormal condition). — The " Micrographic Dictionary" de- 

 scribes only the zoospores in Pediastrum as an a priori argument for 

 their occurrence in the Desmidiacese generally, assuming, erroneously, 

 that genus as belonging to the family. 



A recapitulation of this sort would, however, be incomplete without 

 reference to a communication by M. Ch. Morren in " Annales des Sciences 

 Naturelles," tom. v, p. 266, 1836 — "Memoire surles Closteriees." In 

 looking over the present subject I met with Professor Smith's paper on the 

 "Conjugation of Closterium Ehrenbergii'^ ("Annals of Natural History," 

 second series, vol. v., p. 1), and therefore necessarily with that by M. 

 Morren alluded to ; and it seems to me impossible not to coincide in the 

 conclusions of the former on the points in consideration, and consequently 

 to look upon those of the latter as foimded in error. I shall endeavour 

 briefly to state the views of Morren, as founded on his observations on 

 Cloderinm Ehrenbergii. He believes that in the mature and merely ve- 

 getating plant the cndochromc is evenly distributed throughout its entire 

 cavity, and formed of extremely small granules (" utricles"). By-and- 



