PROCEEDINGS OF SOCIETIES. 173 
Mr. Archer likewise exhibited fine specimens of the various 
stages of conjugation in Closteriwm lineatum, showing its remark- 
able double zygospore; these formed exceedingly striking and 
handsome objects. It was worthy to note the seeming indi- 
vidualisation of the halves of the parent cells which took place, so 
that although self-division had not set in, these halves may be 
regarded as physiologically two distinct cells. In the early stage 
two canals are formed, of course side by side, within which the 
two spores are formed, the adjacent surfaces becoming more or 
less flat-sided by mutual pressure. Nothing could be more exact 
than the fine figure of the mature pair of zygospores and mode of 
attachment of the parent fronds than that given in Ralf’s 
‘ British Desmidiez.’ 
November 15th, 1866. 
Dr. John Barker exhibited a specimen of Arcella dentata of 
seemingly exceptionally pellucid character, thus showing the 
pretty dotted markings and undulate outline to advantage. 
Mr. Archer, in continuation, exhibited a series of rhizopodous 
forms from fresh water, some of which had not yet been recorded 
in Ireland, and one he thought he felt justified in considering the 
type of a new genus. With a view to make the exhibition of the 
series now shown somewhat more explanatory and generally 
interesting, Mr. Archer endeavoured to give a résumé of the system 
of classification of the Rhizopoda adopted by Dr. Carpenter, who 
divides them into three groups, founding, seemingly naturally 
enough, his distinctions on the characters presented by the Pseu- 
dopodia ; thatis, the Lobosa, or those with lobose finger-like pseu- 
dopodia, e. g., Amceba, Difflugia; the Radiolaria, or those with 
exceedingly slender filiform pseudopodia, occasionally somewhat 
branched ; e. g., Actinophrys, Cyphoderia, Euglypha, in neither of 
which groups the pseudopodia become naturally fused on contact ; 
and, lastly, the Reticularia, or those with slender pseudopodia, 
which, on contact, become fused or mutally incorporated, often- 
times in a reticulose manner, frequently irregularly branched, and 
here and there notably expanded, e. g., Gromia, Foraminifera at 
large. 
The examples now exhibited were altogether confined to the 
two former groups.—The Lobosa were represented by various 
Difflugiz and Arcelle. Here, again, Mr. Archer would venture 
to delay one moment to mention that the more frequently these 
creatures presented themselves to him, the more it seemed to 
force itself upon him that they were not things convertible, but 
_ that the same forms again and again turned up; also when cases 
of “conjugation”? were met with, which, at certain periods, does 
not seem a very rare phenomenon, it still always took place the 
same species with the same species, within each particular genus. 
