549 
Dictyota and Taonia. 
zoids, the weather in particular having been very unfavourable 
on account of its dulness and coldness. Even when the 
antherozoids were active, the shortness of their period of 
motility rendered it difficult to make a study of their 
structure. 
When the antheridia are mature, the walls dissolve and 
liberate the antherozoids. If the light is not bright enough, 
or the temperature is too low, or the plant is not sufficiently 
vigorous, they passively float away and get distributed through 
the liquid without showing any signs of motility. This has 
been described by Thuret, Reinke, and other observers. If, 
however, the plants be kept over-night in damp air in a 
darkened chamber, and then placed in sea-water, there is no 
difficulty in getting the male corpuscules to swarm, provided 
it is sufficiently bright and not too cold. This is interesting in 
view of the attempts of Savaugeau 1 to repeat the observations 
of Berthold on the conjugation of planogametes in Ectocarpns 
siliculosns. He found that this phenomenon was only observ- 
able early in the morning, and not even then if the sky were 
dull and cloudy. 
While actively moving, the body of the antherozoid is seen 
to be somewhat similar to that of Himanthalia or of Cystoseira . 
It has not the sharply pointed end so characteristic of Fucus , 
and particularly of antherozoids of Pelvetia ; after fixation 
it becomes perfectly spherical, but during active movement 
it is seen to be somewhat elongated, with one end frequently 
narrower but quite blunt. The movement itself, though at 
first sight similar to that of antherozoids in Fucaceae, has 
peculiarities of its own, which, after a careful examination 
of stained material, we can easily correlate with the character 
of the cilia. 
In most of the experiments, the motility of the antherozoids 
continued for only a short time; about ten minutes being 
the average duration. In other cases, however, some have 
continued in motion for as long as forty minutes. 
1 Journ. de Bot ., X, 1896. 
