268 PROCEEDINGS OF SOCIETIES. 
glass, a shade wider in diameter and rather thinner than an 
ordinary slide, is cemented, thus again closing the aperture 
through the box at one of the surfaces. The upper surface of 
this circle of glass forms the table on which the object for 
examination is placed. At the right hand side, just beyond the 
edge of this circle of glass, and near the lower edge of the box, 
a small hole is drilled through the upper plate of the box, which 
is the feeding hole for the water, which is introduced into the 
box by a small opening ground away at the lower right hand 
corner. The object is now covered by a square of thin covering 
glass in the usual way; one angle of the cover extends at the 
right hand side beyond the circular table, and reaches so far as to 
cover the little feeding aperture in the box, and the flow is estab- 
lished. There is a little strip of glass cemented at the lower 
side to prevent the square cover slipping. This plan has the 
advantage of allowing the light to come up from the mirror, not 
through a stratum of water, however thin, but directly through a 
thin plate of glass, permitting, too, the use of the achromatic 
condenser if needful. Dr. Barker stated he had found this plan 
to act very well. 
Dr. E. Perceval Wright exhibited also Smith and Beck’s new 
modification of Smith’s principle of Growing Slide. 
Mr. Yeates exhibited a soap-bubble under the microscope, 
forming a very gorgeous object, owing to the magnificent and 
ever-changing play of colours which was presented. 
17th May, 1866. 
Mr. Archer exhibited specimens fully conjugated, and in 
various stages of conjugation, of a filamentous form, which at 
first sight might be supposed to belong to the genus Zygogonium, 
as modified and explained by de Bary in his ‘ Untersuchungen 
tiber die Familie der Conjugaten,’ p. 79. But though de Bary 
employs the name Zygogonium, he does not do so in the same 
sense as Kiitzing. The name Zygogonium is one of Kiitzing’s, 
and his genus so denominated may be most briefly defined by 
saying that it comprehends those Zygnemata in which the 
zygospore is formed in the middle space, half-way between the 
conjugating cells; whereas to the genus Zygnema, as understood 
by him, Kiitzing would consign those forms only in which the 
zygospore becomes formed within one of the parent cells, the 
endochrome in both presenting the characteristic doubly stellate 
arrangement. Now, there can be no doubt but that de Bary is 
quite right in doing away with this distinction as a generic one, 
nor would the distinction be, manifestly, at all available as 
regards a barren filament. Therefore, although de Bary refers 
