8 Mr. J. E. Duerden on 
Colour.—The colour of the polyps when retracted is deter- 
mined by that of the vesicles, and may be light blue or light 
brown ; the vesicles, when not fully extended, are generally 
pale blue in colour, the thickened bands and papille a dull 
white, when inflated to their utmost are a pale brown. In 
extension the capitulum, tentacles, and disk are nearly 
colourless, but a slight brown tint can be distinguished ; the 
column-wall in the vesicular region, as well as the pedal disk, 
is brown; the lips white. 
Dimensions.—The dimensions are very variable, according 
to the state of retraction or extension. The diameter of the 
base may be as much as 3°5 centim. ; an average diameter 
of specimens retracted in formalin is 1°8 centim.; height of 
retracted specimens about 0°5 centim.; length of extended 
inner tentacles 3-5 centim.; vesicles when inflated may be 
0:7 centim. in diameter and 1 centim. in length. 
Locality.—The species is met with sparingly throughout 
Kingston Harbour, Jamaica, attached to weedsin shallow water. 
Around the shores of the canal behind Port Royal, and at 
certain other places in the harbour, it occurs in abundance. 
Activities.—The usual condition presented by the animal 
is that of a flattened extended group of bluish-white or pale 
brown vesicles towards the free end of elongated marine 
plants, such as Thalassia, to which the colours offer a marked 
contrast. The polyps are elongated along the length of the 
weed, or partially folded round it, and generally exhibit no 
appearance of disk, tentacles, or column-wall. They well 
bear out Andres’s statement of resemblance to Nudibranchs. 
They occur near the surface in shallow water around the 
shores, and occasionally detach themselves and move to new 
positions, or, more rarely, may float on the surface of the 
water with the base upwards. Less commonly they are fully 
extended, the elongated tentacles in constant motion or grace- 
fully overhanging. The vesicles are very changeable in size 
and appearance according to the amount of inflation; in the 
same polyp some may be inflated and others not at the same 
time ; often they and the tentacles are quite limp. The urti- 
cating powers are considerable, being sufficient to pierce the 
skin of the hand. Itis a very delicate and sensitive species, not 
bearing confinement well. An asexual method of reproduc- 
tion is effected by the detachment of fragments of the body- 
wall from around the margin of the base and column. 
Base (Pl. J. fig. 3).—The three layers of the base are 
clearly distinguishable. The nuclei of the ectoderm are 
arranged mostly in a narrow zone a little below the surface, 
the tissue nearer the mesogleea not staining so deeply. The 
