236 
PROCEEDINGS OF SOCIETIES. 
to do so I have to apologize to those to whom this sketch will, I fear, 
prove tiresome and dry, from being to them so familiar, becanse so devoid 
of novelty or originality. I hope, then, that those who have made these 
or kindred forms a study will bear with me while I try, as briefly as I 
can, to put together a short description of the appearance, nature, and 
position of the group to which I have, on the present occasion, the plea¬ 
sure to add some new species. 
The name “ Desmidiaceae” (taken from the genus Desmidium, con¬ 
sidered as typical), is applied to a group of microscopic organisms, 
undoubtedly a family of confervoid Algae, though, at first, they were asso¬ 
ciated with their kindred family, the Diatomaceae, as one group, con¬ 
sidered by Ehrenberg and his school as animalcules,—and, indeed, I 
believe I would not he wrong if I stated that they were still so considered 
by that illustrious observer. The definition of the “ Diatomaceae” is 
given in Lindley’s “ Vegetable Kingdom” as follows:—“ Crystalline, 
angular, fragmentary bodies, multiplying by spontaneous separation”— 
and of the group so defined the Desmidiae were made a sub-order, dis¬ 
tinguished from the “ Diatomeae” proper, and characterized as “cylin¬ 
drical.” To any one at all acquainted with these two groups of organisms, 
it appears to me that the foregoing definition will not be satisfactory. I 
believe most modern authorities concur in the opinion that the Desmi- 
diaceae are entitled to rank as an order of Algae, separate from hut re¬ 
lated to, the Diatomaceae, which latter order is thus defined by the late 
Professor Smith:—“Plant a frustule, consisting of an unilocular or 
imperfectly septate cell, invested with a bivalve siliceous epidermis. 
Gemmiparous increase by self-division, during which process the cell 
secretes a more or less siliceous connecting membrane. Reproduction 
by conjugation and the formation of sporangia.” Yarious species of the 
large group, thus accurately characterized, are met with in every ditch, 
pond, and stream, and in the sea, some of them very common, whilst 
others occur rarely. They are microscopic cellular organisms, free or 
attached, occurring singly or enclosed in gelatinous tubular investments, 
the individual frustules with yellowish or brownish contents, and pro¬ 
vided with a siliceous coat, which may be broken, but not bent, and 
composed of two usually symmetrical valves with a connecting band at 
the suture, the siliceous coat or shell remaining permanent after the 
organic contents have perished, and often possessing minute and elegant 
markings. They are endowed, many of them, with a power of motion, 
and when this was supposed to be peculiarly an animal function, it is 
not surprising that these beautiful organisms were referred to the animal 
kingdom. They are, however, now almost universally, and there can 
be no doubt correctly, esteemed to belong to the vegetable world, but 
into the discussion it is not the province of this slight sketch to enter. 
It is now my duty to revert to the kindred order, Desmidiaceae. 
Whatever doubt may have existed as to the true nature of the Diatoma¬ 
ceae, I am somewhat at a loss to see how there could have been any he¬ 
sitation with regard to the vegetable nature of the Desmidiaceae. In the 
highest and most recent authority we have on these organisms, Ralfs’ 
