222 ARCHER, ON DESMIDIACE.E. 



question, I will mention what to me appears to be conclusive ; 

 and that is, that in a number of specimens of Cosmcarium 

 [Euastruni ?) sublobatum, also of Cosmarium Botrytis, which 

 had been " mounted " a fortnight, and which we must sup- 

 pose 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 preparation be- 

 come spoiled at the end of the period mentioned. 



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

 have given rise to the following passages : f British Desmidiae/ 

 p. 9, Introduction : " When the cells approach maturity, 

 molecular movements may be at times noticed in their con- 

 tents, precisely similar to what has been described by Agardh 

 and others as occurring in the Confervas. 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. Ralfs, in his work, has 

 to say on the subject; but, although cautiously expressed, 

 it would appear he looked on these minute granules as pro- 

 bably zoospores, and it is, undoubtedly, the same pheno- 

 menon to which he alludes. Hassall, ' British Fresh-water 

 Algse,' 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 swarm- 

 ing granules, as Braun's account of the phenomenon in 

 Pediastrum was not then published. It may, however, be 

 based on Morren's account of the development 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 endochrome, 

 which becomes individualized as in other algse, and so give 

 rise to a new generation. These bodies are figured, with 

 filiform appendages, in Pediastrum granukttum." The first 

 sentence of the foregoing seems to inter that the author 

 looked upon the swarming granules as zoospores, but it is, 

 perhaps, explained by the second, and the statement may 

 be based on what occurs in Pediastrum. — Carpenter, ' The 

 Microscope and its Revelations/ 1st ed., page .-MM : — " Many 

 of the Desmidiaceae multiply after another method ; namely, 

 by the subdivision of their endochrome into a multitude 

 < .;' granular particles, termed gonidia, which arc set free by 



