88 DUBLIN NATUEAL HISTOEY SOCIETy. 



It is true that, unlike A. fdeatus, the aggregated families do not form 

 fagot-like bundles, a character given as generic;'^' but in that species 

 solitarj^ cells, as well as small families of two or four cells, are frequent, 

 the larger number eventually arising from the self-division of a smaller. 

 I have not been able to follow out Niigeli's observations as to the mode 

 of growth in A. falcatus, but in a plant which I refer to Ankistrodesmus 

 convolutus (Corda) — a form I presume to be equivalent to Raphidium 

 minutum (Nag.) — self-division occurred after the same mode as that de- 

 scribed, and the aggregated families consisted of at most eight cells. 

 This was rare, but two and four common ; Nageli referred this (?) plant 

 toEaphidium (Kg.) = Ankistrodesmus (Corda), on d ^rw^' evidence only, 

 as he had not seen its self-division. f 



It may, perhaps, seem somewhat premature to assume my plant as 

 identical with Closterium Griffithii (Berk.) and Closterium sultile (Breb.), 

 seeing that the characteristics relied on by me as generic, in regard to 

 the former, are unknown or unfurnished in regard to the two latter. It 

 is true that in the former instance I found my assumption rather on d 

 jijreor/ evidence, and I cannot, therefore, feel perfectly confident that I am 

 right. My plant agrees with Mr. Berkeley' s in very many ways — in form, 

 in the central pale space, in the absence of moving granules, and in its 

 occurring in long-kept samples of water. It, nevertheless, difii'ers in size, 

 my plant appearing to be smaller ; and Mr. Berkeley's figures indicate a 

 few larger granules in the endochronie, disposed in a longitudinal series. 

 Taking it, however, for granted that I am right in supposing my plant 

 and Mr. Berkeley's to be identical, and that I am also right in my ap- 

 preciation of the generic characters, I should perhaps have used his spe- 

 cific name ; but I may be wrong in assuming their identity, for I con- 

 ceive it not improbable that two organisms might resemble very much 

 in form, but differ in nature, as might be evidenced by their mode of 

 development. Therefore I thought it better not to take his specific 

 name. But any doubt as to ray plant being identical with M. de Bre- 

 bisson's is removed by my having forwarded, amongst others, specimens 

 of my plant to him ; and, in a list returned to me by him of the objects 

 which he had met with on the slides, he includes " C. suhtile," alluding 

 to the very specimens in question. I have not since had the opportunity 

 of having the honour to lay my ideas as to the nature of this plant be- 

 fore him, and consequently cannot say whether he may coincide or not 

 with what I have above laid down in regard to it. It may seem, there- 

 fore, that, if not Mr. Berkeley's, I ought to have adopted M. de Brebis- 

 son's specific name; but as tlacre appears to me so strong a probability 

 that Mr. Berkeley's plant is indeed the same thing, and his name being 

 prior, I thought it, under the circumstances, better to adopt a specific 

 name different from both. 



Seeing that a true generative process (such as conjugation) is un- 



* Ralfs, " British Desmidieae," p.l79. Kiitzing, " Species Algarum," p. 195 

 (Raphidium). 

 t Op. cit. 



