ZYGNEMACE.E. 75 
We append here De Bary’s scheme of classification of this Order, 
which he terms “ Conjugata.” 
“Cells of limited growth, propagated by unlimited repeated biparti- 
tion (tripartite in Craterospermum) in the same direction, free or con- 
nected in single rows, chlorophyll in parietal bands, axile plates, or 
radiating bodies, in pairs. Cell-wall cellulose or gelatinous. 
“ Pructification. By copulation a zygospore arises of a different form 
from its mother-cells. No asexually produced swarmspores. 
“« SUBDIVISIONS, 
“TI. Mesocarpee. Zygospore the shape of the mother-cells, not con- 
tracted, separating by three or five partitions into a central firm-walled 
resting-spore and two or four lateral decaying cells. (Cells cylindrical, 
united in threads, with axile plates of chlorophyll.) 
“II. Zygnemee. Zygospore undivided and mostly contracted, passing 
into the resting condition, afterwards developing into a germ-cell divided 
into a basal cell, and a thread-cell capable of division. (Cells cylin- 
drical, united in threads.) 
“III. Desmidiew. Zygospore of the form of the Zygnemee, develop. 
ing into a germ-cell, or divided into 2 or 4, each of which separates into 
two equal danghter-cells capable of division. (Cells usually consisting 
of two symmetrical halves, of very various form, free or united.)” 
We have adopted a similar arrangement, with the exception of the 
present exclusion of the Desmidiew, and the addition of a small sub- 
family, the Gonatonemee, which dates from a period subsequent to 
De Bary’s Memoir. 
Conjugation in the present family is the union of two cells, either of 
separate filaments, or of the same filament, the result being the forma- 
tion of a zygospore. The cells containing the male and female element 
cannot at present be distingoished from each other, although De Bary 
states that he has observed a constant difference between the fertile and 
sterile cells of a species of Spirogyra. Usually all the cells of one 
filament appear to be either giving or receiving cells, so that the male 
and female filaments would seem to be distinct, but this requires more 
certain confirmation, inasmuch as in such of the species of Spirogyra as 
exhibit lateral as well as scalariform conjugation, all the cells in one 
filament cannot be of the same kind. 
“The first perceptible change in a cell about to produce a resting- 
spore appears to be a loosening of the primordial utricle from the outer 
wall, and a contraction of it upon the cell-contents, which thus are 
crowded together and more or less deformed. Simultaneously with 
this, or a little after or before it, the side wall of the cell is ruptured, and 
a little pullalation or process is pushed out, which directly coats itself. 
with cellulose and rapidly enlarges to a considerable diameter, at the 
same time growing in length until it meets a similar process pushing out 
from an opposing cell, or has attained as great w length as its laws of 
development will allow. When two processes meet they become fused 
together, the end walls are ruptured, and the contents of one cell pass- 
ing over are received within those of the other, or else the contents of 
both cells meet within the connecting tube, and there fuse together. 
This is the more common mode of conjugation, in which two cells of 
distinct filaments become joined together by a connecting tube. It is 
evident that, if the filaments are fertile to their fullest extent, there 
will be as many of these connecting tubes as there are pairs of cells 
in the filaments, and a ladder-like body will be formed, the ori- 
ginal filaments corresponding to the side pieces, the connecting tubes 
to the rounds. Hence this method of conjugation has received the 
name of scalariform. 
“In the so-called lateral conjugation, instead of cells of different 
filaments joining, adjacent cells of one filament unite together to com- 
M 
