90 



Also a species of Nitzscbia from the same place, which form 

 Grunow has described doubtfully as a variety of JV. reversa (W. 

 Smith), (' Verhaudiuugen der Kaiserlich-Koniglicheu Zoolog. 

 Botanischen Gresellschaft iu Wien.,' Band xii, 1862, tab. xviii, 

 fig. 4). This distinguished microscopist had not seen specimens 

 of N. reversa ; if he had, his doubts as to the identity would have 

 been confirmed. This form differs from N. reversa both in outline 

 and in the character of its sculpture, so as to entitle it to be 

 regarded as a distinct species. Mr. O'Meara suggested it should 

 be named N. Grunovii. 



Mr. B. AVills Richardson exhibited one of M. Nachet's cameras 

 for making drawings of objects with the microscope in the upright 

 position, the image being apparently projected in front of the 

 stand. He (Mr. Richardson) spoke highly in favour of the use of 

 this camera for drawing objects iu cells containing fluid ; for, as 

 the slide lies " on the flat," there is but little risk of an object 

 moving, which is so liable to occur during the use of cameras that 

 require the compound body to be at a right angle to the uprights 

 or pillars of the stand. 



Mr. Archer exhibited, new to Ireland, the plane form (var. /3) 

 of Aptogonum desmidmm, or, better, Desmidium aptogo7mm 

 (Breb.). This was taken, very sparingly, from a bog close to 

 the town of Mullingar. It is vevj rare. The triangular form 

 had been recorded from Couoemara last year by Dr. Barker. 

 Nothing could surpass, as a pretty object, a portion ot" a filament 

 of this plane form, for its flatness admits of all coming into focus 

 at once under a quarter-inch. — Mr. Archer likewise presented, 

 new to Britain, Arthrodesmus hifidus (Breb.), and in the same 

 gathering. This is a ver^^ minute ibrm, but one which cannot be 

 confijunded with any other. Artlirodesmus tenuissimus (Arch.) is 

 somewhat like it in front view ; but a side or end view of that 

 form, showing the 2^airs of minute divergent spines, at once 

 settles the matter ; and though these two resemble each other 

 in front view more than either seems to resemble any other form, 

 the bidentate lobes of A. hifidus pi'esents something quite distinct 

 from A. tenuissimus, which latter is a species even still more 

 minute. 



Professor E. Perceval Wright exhibited DeMtella atroruhens of 

 Gray. A small portion of this remarkable organism had been 

 very kindly given to him by Dr. J. E. Gray, who had described it 

 as follows : — " Sponge or coral, dichotomously branched, expanded, 

 growing as a large tuft from a broad, tortuous, creeping base, of 

 a dark brown colour, and uniform hard, rigid substance. Stem 

 hard, cylindrical, opaque, smooth ; branches and brauchlets taper- 

 ing to a point, cylindrical, covered with tufts of projecting horny 

 spines on every side, those on the branches often placed in sharp- 

 edged, narrow, transverse ridges ; those of the upper branches 

 and branchlets close, but isolated, and divergent from the surface 

 at nearly right angles." (' Proc. Zool. Soc. London,' 1868, p. 579, 

 fig. 1, p. 578.) This genus has been placed by Dr. Gray with a 



