124 Dublin Microscopical Club, 
in the latter case evidently the individual zoospores would only be 
approximately about one half the size. It is true, however, that 
the still (thatis, the ordinary vegetative), characteristic examples do 
not usually present any very great differences in size, but maintain 
generally characteristic dimensions. 
Protococcus pluvialis, to show Nucleus.—Dr. M‘Nab showed speci- 
mens of the ciliated state of Protococcus (Chlamydococcus) pluviahs, 
treated with osmic acid and carmine. The nucleus was most clearly 
seen in each free cell, and also in others, which had divided or 
were then undergoing division into four or eight new cells. 
Laticiferous Cells of Euphorbia.—Dr. M‘Nab exhibited a freshly 
prepared specimen of the laticiferous cells of Huphorbia procera; a 
portion of the stem was boiled in dilute caustic potash solution and 
then teased out with needles. 
Polyedrium gigas, W ittrock, a rare Form, exhibited —_Mr. Archer 
further showed Polyedrium gigas, Wittrock, the second time he had 
taken this fine and very distinct form, so large, so bright, so green, 
and so unlike the other rather dull-coloured forms referable to 
Nigeli’s genus, These specimens were from the same county as 
previously, though not the same locality in Westmeath. 
June 15, 1882. 
Ascidiozoids of a Pyrosoma.—Prof. A. C. Haddon exhibited a 
preparation from the Naples Zoological Station, showing four asci- 
diozoids budding off from a cyathozoid, thus forming the foundation 
of a Pyrosoma-colony. He also presented a second preparation, being 
the initial individual of a Botryllus-group in a stage between the 
larva and the adult. 
Stenella, a, s., exhibited.—Prof. E. Perceval Wright exhibited a 
mounted specimen from the ‘ Challenger ’ collection of a new species 
of Stenella, near to but abundantly distinct from S. imbricata, John- 
son; this seems to have been met with very frequently during the 
cruise of the ‘ Challenger.’ ; 
Cosmarium melanosporum, n. 8., with Zygospore.—Mr. Archer 
showed the conjugated state in very considerable quantity of the 
little smooth Cosmarium, with round, very darkly tinted zygospore, 
from which circumstance Mr. Roy and he had agreed to call the 
form Cosmarium melanosporum. This species conjugates pretty 
frequently and always freely; so that, when met with, a large gather- 
ing may thus sometimes be made. 
Elongate unicellular Alga scemingly related to the so-called Cosma- 
rium obtusum, Bréb.—Mr. Archer drew attention to one of those 
unicellular, elongate, more or less curved Alge, believed to be 
generically associated with the so-called Closterium obtusum, Bréb., 
but not properly referred to Clostertwn. The present form is com- 
