CODIUM. BP Arl 
Since the .M.B.C. Memoirs are primarily intended 
for the use of “students of Biology in our laboratories 
and in marine stations,”’ or ‘‘ working privately at natural 
history,’ it may be advisable to summarise briefly the 
main features of the British marine Siphonez, and more 
especially the Codiaces, at the same time indicating the 
general distribution of the species on our shores. 
The British representatives of the Siphonex include 
members of five different orders, viz.: Bryopsidacee, 
Derbesiacez, Vaucheriaceze, Valoniaces, and Codiacee. 
According to Holmes and Batters (A Revised List of the 
British Marine Alge, Ann. of Botany, V., 1890) four of 
these orders are represented in our flora by one genus 
apiece—in each case by the genus that gives the name to 
the order. In regard to the fifth, the Valoniacee, it may 
be noted that the genus inhabiting British seas, viz., 
Halicystis, had not been discovered at the date of the 
publication of Holmes’ and Batters’ paper. 
I. BRYOPSIDACEA. 
The thallus in this order is freely branched in a pinnate 
manner and anchored to the substratum by rhizoids 
which are extensions of the base of the chief axis. The 
branching of the thallus may be bi- or tri-pinnate. Multi- 
plication is effected by the conjugation of dissimilar 
gametes. The female gametes are large and green, the 
male are small and brownish yellow. Both are provided 
with two cilia. The actual fusion of the gametes has not 
yet been observed. No other method of propagation is 
known in the order. 
The Bryopsidacez include only one genus, Bryopsis, 
with about 25 species, chiefly inhabitants of warm seas. 
In British seas two species occur, B. hypnoides, Lamx., an 
inhabitant of the English Channel, and B. plumosa, C. Ag., 
a a ae ae 
