Notes . 463 
inequality of size among the zoospores, and one is tempted to look 
for a physiological distinction between them. 
The unilocular sporangia arise from the cells at the base of the 
cortical filaments, and do not ever seem to arise from the apices of 
the latter. The cortical filaments divide in an irregularly dichotomous 
manner, and in a few cases the apical cell of a filament becomes 
enlarged and divides so as to form two tiers of four cells each ; this 
may represent a stage in the development of a plurilocular sporangium, 
although no intermediate stages w T ere observed. 
Petrospongiwn is closely allied to Leaihesia , differing from it in 
form, consistency, and colour, and being at all stages in its life-history 
solid and fleshy; it would also seem to be nearly allied to Castagnea 
on account of the similarity between their reproductive organs, and 
also to Mesogloia. If we assume that it is not impossible that Meso- 
gloia may give rise to plurilocular sporangia by a modification of 
some of its peripheral filaments, there is no very clear distinction 
between the three genera except one of habit and form, and these 
differences may be the result of a different mode of life. 
Since the researches of Thuret in 1851, very little attention was 
given to the behaviour of the zoospores of these sporangia until, 
in 1881, Berthold demonstrated at Naples the fusion of two zoo- 
spores from the plurilocular sporangia of Ectocarpus stltculosus, thus 
proving that they were true gametes which produced zygotes after 
fusion. The gametes showed a physiological distinction during the 
process of conjugation ; one of them became fixed and lost its cilia, 
while the other remained motile, so that we may speak of the former 
gamete as female and the latter as male. 
Quite recently the accuracy of these statements has been doubted 
by Oltmanns, who attributed them to erroneous observation ; however, 
Sauvageau, and more recently Kuckuck, have succeeded in repeating 
Berthold’ s observations, although Sauvageau says that conjugation 
takes place between the gametes much less frequently than Berthold 
found to be the case, a difference which he considers as depending 
partly on locality and time of year 1 . 
Kuckuck’s experiments with the same plant were unsuccessful : 
but in the autumn of 1897 h e m ade experiments with the zoospores 
from the plurilocular sporangia of Scytosiphon lomentarias , and in 
1 Oltmanns has since withdrawn his objections. Flora, 1899. 
