ARCHER, ON A NEW SPECIES OF ANRISTRODESMUS, 259 



convolutus, Corda — a form I presume to be equivalent to 

 Raphidium minutum, Nag. — self-division occurred after tlic 

 same mode as that described, and the aggregated families 

 consisted of at most eight cells. This was rare, but two and 

 four common ; Nageli referred this (?) plant to Raphidium, 

 Kg. = Ankistrodesmus, Corda, on a priori evidence only, 

 as he had not seen its self-di^dsion.'^ 



It may, perhaps, seem somewhat premature to assume my 

 plant as identical with Closteriwn GriffUhii, Berk., and Clo- 

 sterium subtile, 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 a priori 

 evidence, and I cannot, therefore, feel perfectly confident that 

 I am right. ]\Iy 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 differs in size, my plant appearing 

 to be smaller ; and Mr. Berkeley's figures indicate a few 

 larger granules in the endochrome, 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 appreciation of the generic 

 characters, I should perhaps have used his specific name ; but 

 I may be wrong in assuming their identity, for I conceive 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 my plant being 

 identical with M. de Brebisson'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. subtile," alluding 

 to the vcjy 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 before 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, therefore, that, if not 

 Mr. Berkeley's, I ought to have adopted M. de Brebisson's 

 specific name ; but as there appears to me so strong a proba- 

 bility 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 unknown in Ankistrodesmus, no propagation being known, 



* Op. cit. 



