THE ZYGNEMACEiE. 
817 
Gamoyenesis, or sexual reproduction, finds its simplest 
expression in this humble family of plants. Ordinarily the 
sperm and germ-cells are widely distinguishable ; but here 
no real or perceptible differences of any importance are 
discernible, the two sexual elements being apparently still 
undifferentiated masses of protoplasm. It is true there are 
observers who believe they have discovered some slight 
differences in the two cells. Professor Bennett, in a recent 
communication to the Linnsean Society, affirms that there is 
an appreciable difference of length and diameter, the germ¬ 
cell being the larger ; also that their protoplasmic contents pass 
in one direction only. The first of these statements I might 
be prepared to accept, as it is analogous to what obtains in 
the dioecious species of (Edoyonium; but the fact that in many 
species of the Zyynemace® the contents of both cells pass into, 
meet, and coalesce in the middle of the conjugating canal, 
seems to me fatal to the second statement. However, this is 
a point which must be left to future investigation; still 
it must not be supposed that I absolutely deny that differences 
may exist; on the contrary, I believe that they must, but the 
question is at present involved in obscurity. 
Conjuyation, as the union of the two sexual elements is 
called in these plants, is effected in various ways, but the 
principle is the same in all. At the proper season for the 
species, whether the spring, summer, or autumn, filaments 
lying side by side put out from the opposing face of each cell 
a protuberance of the cell-wall. This goes on increasing until 
the two ends meet. When their opposing faces come in 
contact, fusion, with absorption of the intervening membranes 
at the point of contact, takes place ; there is consequently 
formed a tube or channel of communication from the one cell 
to the other. Whilst this has been going on certain changes 
have been taking place in the contents of the cells. The 
protoplasm lining the cell-walls becomes detached and 
collapses on the central mass. Some observers declare that 
this always commences first in the sperm-cell, or that whose 
contents pass over to the other or germ-cell. However this 
may be, contraction, with expulsion of the water of the cell- 
sap (Sachs), takes place, and the entire contents of the one 
cell pass over, by means of the channel of communication 
described, into the other,* with whose contents it completely 
coalesces, the two nuclei even becoming fused together. As 
Sachs observes (“ Text Book,” 1882, p, 9), “ the coalescence 
gives the impression of the union of two drops of fluid, but 
* Except in those cases where conjugation takes place in the 
conjugating canal. 
