1896. ] BRITISH HYDROIDS AND MEDUS#. ; 495 
TRACHOMEDUS2. 
Fam. GERYONIDA. 
LIRIANTHA APPENDICULATA (Forbes). 
Geryonia appendiculata Forbes (1848). 
Liriope appendiculata, Gegenbaur (1856) ; Agassiz (1862). 
Xanthea appendiculata, Haeckel (1864). 
Liriantha appendiculata, Haeckel (1879). 
This medusa was exceedingly abundant at Plymouth during the 
whole of September and the early part of October, 1893. As 
most of the specimens belonged to the early stages, I was able to 
trace its development. 
First Stage-—Umbrella sub-globose, from 1 to 2 mm. wide, and 
about as long. Velum very broad. On the margin of the 
umbrella there are four interradial tentacles, about half the length 
of the umbrella, and are usually carried in an upright position 
alongside the ex-umbrella. On the inner side of these tentacles 
there are rows of nematocysts, which are directed outwards when 
the tentacle is alongside the umbrella. These tentacles remain 
throughout life. On the ex-umbrella, about one-third the distance 
from the margin, are situated four little, perradial, primary 
tentacles ; each consists of a large cluster of nematocysts upon a 
short stalk. Within the bulb containing the nematocysts there is 
a fine whip-like tongue, which I have seen occasionally protruded 
and after moving rapidly about in every direction withdrawn again 
inside the bulb. These primary tentacles disappear later in life, 
The characteristic features of this stage are the primary perradial 
tentacles and the absence of a manubrium. 
Second Stage—During this stage the manubrium commences to 
grow downwards, a continuation of the edge of the circular 
opening in the first stage. At the same time four perradial 
tentacles commence to grow from the margin of the umbrella. 
They differ considerably from the interradial tentacles, and are 
not carried in an upright position, but hang down or trail behind 
the umbrella when the medusa is in motion and can be extended 
to a considerable length. Each tentacle has numerous rings of 
nematocysts. The lateral primary tentacles on the umbrella are 
usually present, but one or two may be absent. Medusa belonging 
to this stage may be characterized by possessing four perradial 
tentacles on the margin of the umbrella, and a short manubrium, 
not reaching to the velum. Umbrella about 3 mm. in diameter 
and colourless. 
Third Stage.—This is really the commencement of the adult 
stage, as the gonads begin to develop upon the radial canals. The 
lateral tentacles disappear and small scars mark their former 
position upon the ex-umbrella. The manubrium extends slightly 
beyond the cavity of the umbrella. Umbrella about 4 mm. in 
diameter. I have divided the early stages into these three 
