420 Mr. R. Vallentin on the Dispersal of 
species of seaweed were obtained either in the bay or harbour, 
where they were drifting about in the tideways after being 
detached from their respective habitats by the force of the 
waves. 
As my most interesting results have been obtained from 
the class Mollusca it will be convenient to take my starting 
oint from those animals. Mr. Wallace (1)*, under the heading 
of “‘ Means of dispersal of Mollusca,” writes as follows :-— 
“The marine, fresh-water, and land mollusca are three groups 
whose powers of dispersal and consequent distribution are 
very different and must be separately considered. The 
Pteropoda and Janthina and other groups of floating mollusks 
drift about in mid-ocean, and their dispersal is probably 
limited chiefly by temperature, but perhaps also by the pre- 
sence of enemies or the scarcity of proper food. The univalve 
and bivalve mollusca, of which the whelk and cockle may be 
taken as types, move so slowly in their adult state, that we 
should expect them to have an exceedingly limited distribu- 
tion ; but the young of all these are free-swimming embryos, 
and they thus have a powerful means of dispersal, and are 
carried by tides and currents so as ultimately to spread over 
every shore and shoal that offers conditions favourable for 
their development.” Prof. W.Sollas (2) remarks as follows :— 
‘‘Perhaps one of the commonest ways by which marine 
animals obtain a distribution over extensive areas is by means 
of free-swimming larva. ‘The peopling of the sea by slow- 
moving or attached forms has certainly been accomplished 
chiefly, if not almost wholly, in this manner.” 
I have been fortunate enough to secure two specimens of 
bivalve mollusks while being dispersed by floating seaweed ; 
and, strange as 1t may appear, one was a specimen of Cardium 
edule, a long frond of Chorda filum being attached to the left 
valve by its base. ‘This mollusk was secured a mile from 
land, and was found on examination to be alive and in a 
healthy condition. Unfortunately this specimen and the 
attached weed were placed after examination on the deck of 
my canoe, and were washed overboard by a wave. A short 
time later a fine living example of Mytelus edulis was secured 
under similar circumstances and weighed 23°3 grms. The 
weed, Chorda filum, was also in this instance firmly fixed to 
the left valve; it measured 310 centim. in length and weighed 
43°3 grms. Had these mollusks escaped the notice of cod, 
pollock, or other fish which frequent the mid-water regions, 
they might have been carried by the currents on some shoal 
or bank, and so founded fresh colonies. 
As Chorda filum invariably floats vertically, I have found 
* These numbers refer to bibliographical list at end. 
