205 



lected during the voyage of H.M.S. Simoom to Ascension, in the 

 months of October and November last. The specimens illustrated 

 the peculiar fact that these cillo-flagellate Infusoria constantly 

 occur connected together in chains composed of from two to eight 

 or more individuals, generally, but not invariably, lessening in size 

 from above downwards — that is to say, towards that end of the 

 chain which presents the Ceratium with a free stock. Their 

 attachment depends upon the reception of the extremity of the stalk 

 of one into a little cup-shaped hollow in the fiat surface of the body 

 of the other, on the side opposite to that which presents the flagel- 

 lum, and at the termination on that side of the cestoid ciliated groove, 

 "When a Ceratium tripos in a drop of water is placed upon a 

 glass slide, it usually lies on its flat or slightly concave surface, 

 with the upper angle of the carapace and the greater cornu spring- 

 ing from it to the left. In this position the ciliated groove, passing 

 ti'ansversely across the convex surface of the body, divides it into 

 two nearly equal portions, through the upper of which, close to the 

 root of the right cornu, the attached stem of the next individual of 

 the chain can be seen ; and on the left side, in a somewhat corre- 

 sponding position, a folding-in of the integument forms a canal for 

 the flagellum, which is extended through an oral opening in the 

 carapace, internal to the first serrations (in some varieties very 

 prominent) on the base of the left cornu. It is, perhaps, worthy 

 of remark that no exchange of endochrome between the connected 

 infusoria has been observed, and that two varieties of Ceratium 

 have never been found in the same chain. 



Dr. E.. M'Donnell exhibited preparations of nerves, which were 

 much admired. 



Dr. Archer exhibited a very pretty, seemingly new, Cosmarium, 

 which most approached C cristatum, Ralfs. Ealfs' description of 

 that species, examples of which he had not himself seen, was made 

 from drawings furnished to him by Sidebotham. Relying on their 

 accuracy, the present appeared to be distinct from that rare species. 

 In the present there are four lines of processes bordering the cell ; 

 not two only, but these prominences of but one kind. The form 

 appears to be stouter and thicker than G. cristatum, whilst the 

 little prominences ornamenting this pretty form are distinct from 

 those belonging to any other in this genus — except, perhaps, C. 

 cristatum — in that they are neither " pearly" granules nor spines, 

 but short, thin, compressed, quadrate, vertical processes, the upper 

 outer margin emarginate ; thus, to a greater extent, resembling the 

 similar ornaments of the Staurastrum exhibited by Mr. Archer at a 

 former meeting of the club (^Staurastrum maamense). A more 

 detailed account of this pretty form, gathered by Dr. Wright at 

 Griengariff, on a late visit thither, Mr. Archer hoped to be able to 

 present on some future occasion. 



