DUBLIN NATUKAL HISTOKY SOCIETY. 27 



But if further evidence were wanting to prove the point in question, 

 I will mention what to me appears to be conclusive ; and that is, that 

 in a number of specimens of Gomiarium {Euastrum ?) sublohatum, which 

 had been "mounted" a fortnight, and which we must suppose to have 

 been dead, I have witnessed the granular cell-contents exhibiting the 

 "molecular" movement as actively as it occurs in the living frond; and 

 this might have been kept up while I write, possibly, had not the pre- 

 paration become spoiled at the end of the period mentioned. 



Such, then, is, I apprehend, the phenomenon which may have given 

 rise to the following passages: — "British Desmidia3," p. 9, Introduc- 

 tion : — " When the cells approach maturity, molecular movements may 

 be at times noticed in their contents, precisely similar to what has been 

 described by Agardh and others as occurring in the Confervaa. This 

 movement has been aptly termed a swarming. . . . When released by 

 the opening of the suture, the granules still move, but more rapidly and 

 to a greater distance. With the subsequent history of these granules I 

 am altogether unacquainted, but I conclude that it is similar to what has 

 been traced in other algae." This brief passage is all Mr. Balfs in his 

 work has to say on the subject, but, although cautiously expressed, it 

 would appear he looked on these minute granules as probably zoospores, 

 and it is, undoubtedly, the same phenomenon to which he alludes. Has- 

 sall, "British Fresh- water Algae," p. 340: — "The second method is, 

 assuredly, the usual and legitimate mode of reproduction, viz. that by 

 bodies analogous to zoospores." This statement surely appears to be 

 founded on the molecular movement of the minute swarming granules, 

 as Braun's account of the phenomenon in Pediastrum was not then pub- 

 lished. It may, however, be based on Morren's account of the develop- 

 ment in Closterium, to which I shall presently allude. — Berkeley, 

 "Introduction to Cryptogamic Botany," page 121 : — " Another mode of 

 increase is from the swarming of the grains of the endo chrome, which 

 becomes individualized as in other algae, and so give rise to a new genera- 

 tion. These bodies are figured, with filiform appendages, in Pediastrum 

 granulatumP The fii'st sentence of the foregoing seems to infer that the 

 author looked upon the swarming granules as zoospores, but it is, per- 

 haps, explained by the second, and the statement may be based on what 

 occurs in Pediastrum. — Carpenter, " The Microscope and its Bevela- 

 tions," 1st ed., page 291 — "Many of the Desmidiaceas multijily after 

 another method; namely, by the subdivision of their endochrome into a 

 multitude of granular particles, termed gonidia, which are set free by 

 the rupture of the cell- wall, and of which every one may develop into 

 a new cell. These * gonidia' may be endowed with cilia, and many pos- 

 sess an active power of locomotion, in wliich case they are known as 

 ' zoospores;' or they may be destitute of any such power, and may be- 

 come enclosed in a firm cyst or envelope, that seems destined for their 

 long- continued preservation, in which case they are designated as * rest- 

 ing spores.' — The movement of the zoospores, first within the cavity of 

 the cell that gives origin to them, and afterwards externally to it, has 

 frequently been observed in the various species of Cosmarium, and has 



