148 NATURAL HISTORY SOCIETY OF DUBLIN. 



Freshwater Algae of Franconia,'* it is stated by that writer — "The 

 position of the Spirotaeniae in the system is still very uncertain ; they 

 belong, with Eremosphaera, most probably to the Palmellaceae." 

 Again, in de Bary's work on the Conjugate, as regards this genus, he 

 states — " On account of the fructification being unknown, the position 

 of the entire genus is not quite certain, "f 



That this genus should be relegated to the Desmidiaceae will, I 

 think, be considered proven from the following description of the con- 

 jugated state, as it differently presents itself in two distinct species, 

 now for the first time recorded, and this notwithstanding Eeinsch's 

 views expressed on the conjugation in Palmogloea,J a genus he still re- 

 tains, notwithstanding de Bary's beautiful researches. § 



Before, however, proceeding to describe the conjugation of S. con- 

 densata, it would seem to me to be desirable to draw attention to the 

 seemingly noteworthy fact, that in this species the nucleus is parietal, 

 not central. It forms a somewhat large elevation, rounded on one side 

 and straight on the other, the convex side projecting into the cavity of 

 the cell and gradually sloping off all round, and its flat side towards 

 the wall ; it is ordinarily placed equidistantly from either end of the 

 Spirotaenia. It has imbedded in the very centre a minute, light- 

 coloured, distinctly marked nucleolus. The broad spiral band of 

 endochrome, in making its revolutions, twice underlies the body of the 

 nucleus, which fact will convey an idea of the extent of space covered 

 by its flat side. The nucleolus always occupies a position just over the 

 vacant interval between the two parts of the spiral band which under- 

 lie the nucleus, thus the more readily disclosing itself to view, as there 

 is there no chlorophyll-mass intervening to obscure or hide it. 



The figure described for the nucleus is, of course, that presented by 

 it when seen from the side ; when seen from above or below it natu- 

 rally offers a rounded outline, and might then be readily taken as a 

 globular and central nucleus. 



It must be noted, however, that this characteristic of the nucleus 

 is plainly to be seen only in specimens kept for some time in the house ; 

 in such examples the band of endochrome becomes much more sharply 

 defined, with a smooth edge, like a little ribbon — those granules, which 

 ordinarily are more or less scattered, and which thus tend in a certain 

 degree to obscure the actual characteristic spiral arrangement of the 

 endochrome, seem then to be absent — then the nucleus and its nucleo- 

 lus come out to view in perfection. Indeed, it is hardly possible to 

 see a more elegant object than a favourable specimen of this handsome 

 species, which shows the nucleus in side view and the light so shed 

 from the condenser as to fully illuminate the whole cavity, and clearly 

 to display its characteristic and beautiful arrangement. 



* " Die Algenflora des mittleren Theiles von Franken," p. 203. 

 f " Untersuchungen liber die Familie der Conjugaten," p. 75. 

 % Reinsch, op. cit., p. 202. 

 § De Bary, op. cit, p. 30. 



