DUBLIN NATFllAL HISTOEY SOCIETY- 89 



known in Ankistrodesmus, no propagation being known, save mere self 

 division in the manner described, the position of the genus is therefore 

 doubtful. 



Probably, for the present, it is best to consider it as a doubtful or 

 aberrant genus of Desmidiaceae. Its oblique self-division, so far as it 

 goes, is somewhat like that of Spirota3nia ; but there is no further resem- 

 blance. JN'ageli* and Eabenhorstf place Eaphidium (equivalent to Ankis- 

 trodesmus) amongst Palmellacese ; but the very elongate acute cells are 

 very unlike anything else in that family. De Bary;}: alludes to this genus 

 as doubtfully Desmidian. - 



Assuming that I have proved my plant to be a true Ankistrodesmus, 

 and not a Closterium, it may be weU to compare it with the other ad- 

 mitted species of that genus. It agrees yiriih. A. falcatus in its very slender 

 and acute cells, but it differs from it by its straight, not arcuate cells, 

 by its fusiform, more -quickly attenuated cells, by its more intensely 

 acute extremities, and by the constitutent cells of an old fasciculus being 

 much fewer in number. It is, indeed, a very different plant. This 

 form scarcely agrees at all, except generically (as I think), with A. con- 

 vohdus (Corda), the cells differing as they do in their very slender (not, 

 comparatively, stout) form, in their straight (not crescent-shaped) out- 

 line, and in their extremely acute extremities. With A. contortus (Thuret) 

 this form agrees in the very acute cells ; but it differs in their straight 

 (not arcuate or sigmoid) form, and in the cells being not inflated at the 

 middle. 



I have m the foregoing remarks alluded to the distinctive characters 

 of Closterium and Ankistrodesmus as regards the mode of self-division. 

 I conceive it may be quite worth while, in connexion therewith, to draw 

 attention to a remarkable state of Closterium acutum (Breb.), (it may be 

 C. suhulatum (Breb.), but I am disposed to think these are synonymous). 

 This consists of a curious aggregation of fronds of that Closterium into 

 chains and bimdles in the manner I represent in the accompanying sketch 

 of some of the most remarkable of these cases (Figs. 58 to 60). The fronds 

 were sometimes juxta-posed side by side, sometimes irregularly, at other 

 times combined into a kind of chain, while multitudes of fronds, in the 

 ordinary free condition, abounded in the gathering. This, whatever it 

 portend, was no accidental juxta-position; for they, not unfrequently, 

 in order to accommodate themselves to one another in the combina- 

 tion, were of a sigmoid, or otherwise curved and bent character, yet no 

 gelatinous matrix was apparent, and I cannot say what may have held 

 them together. Of the meaning of this very remarkable condition 

 I cannot form any idea, except to guess the possibility of its being an 

 approach for the purpose of conjugation, on a scale, indeed, wholesale. 

 No alteration took place either m their internal or external appearance, 

 though kept for some time ; and I then, unfortunately, lost the speci- 



Op. cit. f "Algen Sachs." 



" Untersuchungeu iiber die Familic der Conjugaten," p. 77. 



