DUBLIN NATURAL HISTOEY SOCIETY. 85 



longing to Spirotasnia ; but as it frequently seems to form an oblique 

 parietal band, and the self-division, as in other species of the genus, is 

 oblique, and the divided fronds held together by a gelatinous invest- 

 ment, there can, I apprehend, be no doubt but that in this genus this 

 minute little form finds its proper location. Moreover, I have seen some 

 specimens in which the endochrome clearly made a spiral turn, though 

 in the majority of instances the condition I have tried to describe above 

 is seen ; and not unfrequently, as in other species, a confused or irregular 

 condition of the endochrome exists. Its very minute size, subacute ex- 

 tremities, and without a clear space, easily distinguish this from other 

 described species of Spirotsenia. It really appears to approach more to 

 Entospira closteridia (Breb., Kg.), (which plant, as I before stated, I 

 apprehend should faU under this genus) ; but it is distinguished by its 

 fusiform, not at all arcuate, and by its narrow, outline, as well as by its 

 obscurely convoluted, not distinctly and smoothly spiral endochrome. 



Mr. "William Archer also read the following paper : — 



ON A NEW (?) SPECIES OF ANKISTRODESMUS (cORDA), WITH REMARKS IN 

 CONNEXION THEREWITH AS REGARDS CLOSTERIUM Gi^EEITHII (bEEK.), * 

 AND C. SUBTILE (bREB.). 



I HAVE, on the present occasion, to draw attention to a very minute orga- 

 nism, but which, indeed, so far as I can see, I can scarcely allude to as a 

 new species ; for I conceive that it has been more than once previously de- 

 scribed, but I think I shall be able to render it probable that it has been 

 so under an erroneous designation. Of course, the truth of this assump- 

 tion depends on my being right as to the identity of my plant with that 

 of the authors alluded to, as well as upon my own proper appreciation 

 of its characteristics, and the correctness of my own conclusions in re- 

 gard to them. I shall now, however, give the characters of the plant 

 according to my own view, adopting, in doing so, the same mode that 

 I have done in other species, reserving the reasons why I venture to 

 difi*er from those who have previously described what, as I before stated, 

 I conceive to be one and the same organism, for the paragraph which I, 

 as previously, head "Affinities and Differences." 



Generic Characters : — Cells minute, smooth, elongated, attenuated, 

 more or less numerously aggregated, forming fasciculi, or families ; each 

 family resulting from the self- division of a single cell, which commences 

 by the formation of a somewhat oblique septum at the middle, continu- 

 ally rendered more and more oblique from the young cells growing along- 

 side one another longitudinally until they each attain the length of the 

 original parent cell, the process being again and again repeated by each, 

 till the aggregated family consists of at most thirty-two cells, the family 

 finally again breaking up into single cells (Nageli).* 



Gattungcn einzelliger Algcii," pp. 82-3. 

 N 



