86 



the diameter did not greatly exceed that of tlie bristles of the 

 Bulboclicete setigera ; but their distinct appearance and jointed 

 nature, with the apparent fruit-cells, were quite evident on apply- 

 ing a power sufficiently high. 



Mr. Archer, thanks also to Mr. Reeves, exhibited examples from 

 England of the " water-net" {Jlydrodklyon titriculatum) . This 

 remarkable alga has never yet been found in Ireland. 



Dr. John Barker exhibited a remarkable little Infusorium, clearly 

 a new species, if not, indeed, the type of a new genus. This was 

 minute, pear-shaped, mostly green, covered by scattered vibratile 

 cilia, those at the extremities being longer and more prominent 

 than the rest, at one side furnished with an almost semicircular, 

 vibratile, constantly undulating flap. The green colour was due 

 to the presence (imbedded in the substance of the body) of 

 numerous chlorophyll-granules, but this form has been occa- 

 sionally met with colourless. This little animal inhabited an 

 elongate, barrel-shaped, hyaline glassy test, open at both extremi- 

 ties, in which it could freely move and completely turn round and 

 round. This test appears, at first at all events, to be attached by 

 the side to various filaments, but is often met free. A part of the 

 exercise of this creature appeared to be performed in spinning 

 itself round and round on its longitudinal axis, like a top, and 

 another part in efforts to push itself through the opening at one 

 end of the test, speedily turning round and driving itself strongly 

 BO as to partially emerge at the other end. It even sometimes 

 succeeded in swimming away, and the empty " barrels" were 

 Bometimee met with in the water. The animal seemed to divide 

 by transverse fission. A more detailed account of this remark- 

 able, though very minute little creature, will be prepared by 

 Dr. Barker for a future occasion. 



Dr. Barker exhibited a Staurastrum, taken by him in Co. 

 Westmeath, presenting the peculiarity of having but two arms 

 in end view, but which had all the aspect in front view of Stau- 

 rastrum gracile, from which it thus differed in being plane, not 

 triangular. This circumstance rendered this form a very pretty 

 object, because, being so nearly flat, all its superficies, arms and 

 all, could be simultaneously brought into focus, aud thus seen to 

 perfection. Dr. Barker was inclined to regard this comj)ressed 

 form as a species distinct from any other, even St. gracile. 



From the latter view, expressed by Dr. Barker, Mr. Archer 

 observed that he as yet could not but difter ; he regarded tliis as 

 a singular and interesting form of Staurastrum graciJe, and would 

 even venture to foretell that if the pools whence these specimens 

 had come were searched the triangular form might disclose itself. 

 These examples were just an additional proof of the view he had 

 long entertained, that the forms generally referred to the second 

 section of the genus Arthrodesmus (Ehr.) were, strictly speaking 

 and naturally, but plane or two- (not three-, four-, or more) 

 sided Staurastra. He was well acquainted with a very minute 

 and slender triradiate tStaurastrum, which he regarded as nothing 



