40 CRITICAL NOTES ON SOME SPECIES OF DIATOMACEiE. 



The markings on Cyjnbella, liowever, differ from those on the 

 Cocconemeta sufficiently, perhaps, to warrant their separation; those 

 on the latter are distinctly moniliform, whilst those on the former 

 are apparently costate. I say apparently costate; they are really 

 not so ; when examined with a high power and oblique light they 

 will be found to be composed of a series of compressed beads. 



C. Ehrenbergii, when thus illuminated, is an object of considerable 

 beauty. 



Synedra irobusta (Ralfs.) — The conspicuous striae on this species, 

 when examined with the oblique light, will be found to be composed 

 of a series of beads very much compressed. F. Kitton. 



NOTE OF THE OCCURRENCE IN IRELAND 

 OF THE MINUTE ALGA, CYLINDROCAPSA INVOLUTA. 



By W. Archer. 



The occurrence in this country of Cylindrocapsa invnluta, Reinscli. 

 (" Die Algenflora des mittleren Theilcs von Funken," p. 6G, t. vi-, 

 f. 1), will possibly interest the alg >Ingical rea<lers of this journal, 

 although the plant itself is not one of any striking appearance. 



Admitting the identity, of which 1 myself do aot doubt, though 

 not previously having seen examples, that .luthor's description of 

 this minute alga does not appear quite complete, as he omits to 

 mention that the cylindrical hyaline envelope of the cells, combin- 

 ing them into a frond, is closed at both extremities, rounded off at 

 the upper, and somewhat produced, tapered and thin, slightly di- 

 lated into a scutate organ of attachment (to foreign objects) at the 

 lower extremity. Thus the extremities appear to be differentiated 

 into a basal and apical. The Irish plant agreed with Reinsch's in 

 the dimensions of the cells, their oval figure (truncate after division, 

 whilst closely apposed, and until full size is again attained), their 

 longer diameter posed in the direction of the length of the cylin- 

 drical filament and in their being involved by a number of con- 

 centric hyaline investments standing off from the cells at the poles, 

 closely applied at the sides; not, however (as Reinsch shows) uni- 

 formly /b«r, but two, three, or four, and standing off from the cells, 

 not equidistantly, but at different distances. It is, however, quite 

 possible that where the fewer number only of laminae of the enve- 

 lopes were apparent, others may have been present, but so closely 

 applied to the cells (and to each other) as to appear as if absent. 

 Just as depicted by Reinsch (though his figure be rather stiff). I 

 saw some of the cells undergoing self-division, the fission always 

 taking place through the shorter diameter, the new cells, at first 

 flattened at the ends, then growing as long as the older, and be- 

 coming rounded off, and thus the longitudinal direction of the cells 

 is maintained. Thus this form is unlike Cylindrocapsa nuda 

 (Reinsch), in which the oval cells are placed transversely, and 



