160 HISTORY OF BRITISH ZOOPHYTES. 
2. LAOMEDEA GENICULATA, Knotted-thread Coralline, 
Doody. (Plate X. fig. 31.) 
Hab. On Laminaria, very often on Halidrys siliquosa, 
and not unfrequently on Chorda filum. ‘Some of the finest 
specimens I have seen were growing on the dorsal and 
caudal fins of a picked dog-fish.” (Cowch.) 
It is interesting to observe how indissolubly the fibrous 
roots of this coralline are twined round the branches 
of the Haldrys. And though a person would suppose 
that it would not be able to fasten itself firmly on the 
smooth frond of Laminaria, he will find, on trial, that it is 
no easy matter to detach it. The fibres, half-sunk in the 
frond, “ form,” as Mr. W. Thompson observes, “a regular 
piece of network, having meshes of various size, with their 
junction tied in a knot, as it were by fairy fingers: from 
each knot, in due time, the zoophyte s>rings.” 
The polypidom is about an inch in height, zigzag, the 
cells bell-shaped ; the vesicles somewhat resemble an urn in 
form. Several naturalists have observed that this coralline, 
like several others, is often tinted with red; but it has not 
been ascertained on what the red colouring depends. We 
think that we have at times observed that it is a slight film 
of Melodesia. 
