Marine Animals by means of Seaweeds. 419 
north-west or north, and if the sea has reached a higher level 
than before the change of wind occurred, large masses of 
various species of seaweed can be observed being carried to 
sea by the wind arid tide during the following ebb. In 
addition to this I have quite recently noticed in the numerous 
ereeks with which Falmouth harbour abounds single shells 
and stones resting on the muddy or sandy sea-bottom with 
specimens of Yucus of various sizes attached to them in a 
flourishing condition. In every instance the weed is able to 
maintain a vertical position in the water owing to the pre- 
sence of the numerous air-vessels on the fronds. In some 
cases the weed is so large that it can almost float the stone 
or shell on which it is growing; in others, some time will 
have to elapse before that can beaccomplished. Without much 
difficulty during any calm day at low-water one can secure 
similar specimens in all stages of growth. 
Attention may here be directed to the rate of flow of the 
retiring waters during ebb-tides. [ am informed by the 
pilots frequenting this port that under favourable conditions 
a floating body such as a mass of seaweed would easily be 
driven five miles from the harbour during an ordinary ebb- 
tide. If, however, this were supplemented by a fresh north 
or north-west wind these floating masses would be driven 
even beyond that limit. Possibly one tide would be spent 
before the influence of the shore currents would be lost on 
these floating objects, and before the channel tides would be 
able to exert their influence on them; but when once these 
latter came into play there is no knowing where they might 
be swept to. 
Before proceeding further, I will now record some experi- 
ments I have made as to the powers of flotation of some of 
our common seaweeds in sea-water. I have had portions of 
Fucus nodosus floating in vessels of sea-water for eleven and 
a half weeks, and J. serratus for upwards of seven weeks. 
On the other hand, Fucus vesiculosus never floated longer than 
five weeks. Specimens of Halidrys siliquosa floated in some 
instances for three weeks, and other examples for as many 
months. Many specimens of Zostera marina were found to 
float never longer than three days; they then invariably 
sank to the bottom of the jar in which they had been placed. 
Attempts were also made to discover how long the fronds of 
Chorda jilum remained floating in the water, and during calm 
days several examples were moored in very sheltered places 
in the harbour. But these experiments were invariably 
unsuccessful, mainly owing to the surface-motion produced 
by passing steamers. I may mention that all these various 
