70 
Smith on Asteridia. 
process occurring in two cells belonging to different fila- 
ments. The mode in which this amalgamation takes place 
is either bj the breaking down of the walls at the contiguous 
extremities of the cells, as in the Vesiculifercp, or by the 
production of connecting tubes, which form channels of com- 
munication between the conjugating cells, whether in the same 
or different filaments. These connecting tubes are shown in 
the drawings which accompany this paper, PI. IX., fig. 2 b, 
fig. 4 h, Sec : and it is worthy of notice that, although one 
mode of effecting the union of the cells seems to be pretty 
general in the same Al^a, it is by no means constant, as tubes 
connecting contiguous cells of the same filament, or uniting 
apposed cells of different filaments, will be found in con- 
nexion with the same species : an example is given in fig. 6.* 
Now it will be seen by a reference to the figures I have 
given, and more particularly to figs. 4, 5, 6, which are drawn 
with the camera lucida from mounted specimens of Zygnema 
quadratum kindly supplied by Mr. Shadbolt himself, that the 
circumstances, as stated above, which accompany the process 
of conjugation, altogether negative the opinion that the 
asteridia are products of such a process, as the cells contain- 
ing these bodies always contain with them a portion of the 
original endochrome or cell-contents, which must have been 
entirely absorbed had conjugation been effected. Nor are 
there, in any case, to be found the connecting tubes which 
are necessary to the process in the species we have selected. 
It is, therefore, evident that the asteridia are not modified or 
matured spores, as the cells containing them have not under- 
gone the process necessary to the formation of the repro- 
ductive body. 
An inspection of fig. 1 will also show the incorrectness of 
the conclusion to which Mr. Shadbolt has arrived, viz., that 
the asteridia are spores in a more advanced stage. We have 
here a portion of a filament of Zygnema quininum, in the cells 
of which the gradual formation of the asteridia may be dis- 
tinctly traced. Cell a presents the ordinary and healthy ap- 
pearance of the plant ; in cell b degeneration has commenced, 
and a faint appearance of several aggregations of the cell- 
contents may be detected ; these aggregations in cell c assume 
the character of perfect asteridia, which in cell d are no 
longer in contact with the endochrome, among which they 
have been generated. But in no case do we perceive any 
* This fact throws some doubt upon the propriety of placing (as Kiitzing 
has done in his genus Bhynchonema, and Hassall in a sub-genus) species, 
which conjugate by tubes connecting contiguous cells, apart from those 
in which the conjugation takes place between cells in different filaments. 
