293 PROCEEDINGS OF SOCIETIES. 



characteristic of the genus to which tliis common ami fine form 

 appertains (not two such, as ])erhaps might be anticipated). 



Rev. E. O'Meara exhibited a very curious and interesting new 

 diatom appertaining to the genus Amphiprora, and obtained from 

 the contents of the stomach of a Holothurian from the Sejchelle 

 Ishmds, taken by Dr. E. P. AV right, and it occurred therein not 

 unfrequently. This at first somewhat puzzling form was named 

 by Mr. O'Meara Amphiprora rimosa, and described as iollows : — 

 Valve constricted; length, '0070" ; greatest breadth, 'OOSS''; breadth 

 at the constriction, •0C2G". The central line at about three fifths of 

 its length diverges slightly, and, again bending back, proceeds to- 

 wards the apex ; at one end of the valve this divergence takes plaae 

 towards the right, at the other towards the left ; at the point of di- 

 vergence the line sends out two branches, alternately disposed, and 

 one somewhat longer than the other; the longer branch curves 

 towards the apex, the shorter is straight. Further on, the line 

 forks, one branch, as in the former case, being longer than tlie 

 other, the longer being also curved towards the apex. The longer 

 and shorter branches are arranged on one side of the line in one 

 portion of the valve, and at the opposite side on the other. Striae 

 linear, fine, disposed in nearly parallel curves around the extremi- 

 ties of the branches of the central line ; the keel is ornamented 

 with a row of moniliform dots. More enlarged description, with 

 illustration, of this fine form, as well as others, are in preparation 

 by Mr. O'Meara, to appear on a future occasion. 



Mr. Archer wished to mention having seen the escape of the 

 monad-like body from the encysted condition of Dinohryon sertu- 

 laria. This encysted condition has been described by Hermann 

 (in Eabenhorst's ' Beitrage zur naheren Kenntniss und Verbrei- 

 tung der Algen,' Heft i), and Mr. Archer had once had an oppor- 

 tunity of showing some specimens at a meeting of the Club ; but 

 the escape of the contents seems to be a new fact, so far as it goes. 

 The globose cyst at the mouth of the well-known campanulate 

 carapace of the Dinobryon becomes tilted up, and the monad or 

 zoospore-like body escapes through an opening, which terminates 

 a projection previously pointing into the mouth and towards the 

 bottom of the carapace, which is thus left behind. Nuuibers of 

 these cysts, empty and separated, others still attached to the cara- 

 pace, occurred in the water; few colonies remained combined as 

 in the ordinary condition, but were broken up nearly altogether 

 and scattered about in some abundance. 



Mr. Archer placed on the table a number of Desmidiea^, showing 

 their zygospores, some of them not hitherto seen in that condition, 

 others rarely so. 



The zygospore of Closterium gracile (Breb.) is new, but is very 

 like that of C.juncichmi, that is, it is orbicular or broadly elliptic 

 and smooth, and placed between the four halves of the pair of 

 mother- cells, which are all pushed asunder by the interposition of 

 the spore. Mr. Archer thought that, although the form and general 

 character of the zygospore in many of the species of Closterium 



