Journal of the 
46 
On Scrupocellaria scrupea, another genus of the Cheilostomatous 
Polyzoa, there is another organ, the use of which in the economy 
of the Polyzoa is also uncertain. It is called a vibraculum, and 
consists in this species of a long spine attached to a socket joint, 
on which it can move in any direction, and with considerable force. 
Busk asserts that, in the majority of cases observed, this organ is 
mainly defensive in its character. In the few instances that came 
under my notice, they seemed to be used purely for cleansing. In 
Scrupocellaria , the motion of the vibraculse was continuous, rising 
upwards and outwards with a slow, steady motion, and then back 
with a sudden jerk, as if by the snap of a spring, the jerk being 
downwards across the cells at back or front, sometimes alternately, 
thus apparently sweeping the surface of the cells free from any 
particles whose presence might disturb the comfort of the Polyzoon . 
This species was not so liberal in the display of its beauties as 
others had been, the tentacles being seldom fully extended, but 
I was enabled to ascertain that their number was invariably 
twelve. 
Emma crystallina had also twelve tentacles. This is a very 
difficult species to make out, owing to the peculiar way in wliich 
the branches of the Polyzoary curl inwards. The cilia on this 
species are very short, so that it requires a power of about one 
hundred diameters to observe them with any clearness. 
In most species of the Ckeilostomata, the polyzoon only extends 
from its cell the lophophore or collar bearing the tentacles. In 
Eucratea chelata , however, tentacles twelve, nearly the whole 
animal would be extended. Not only the gullet, but almost the 
whole of the stomach could be observed outside the cell mouth. 
From this circumstance, and also owing to its extreme loveliness, 
this species is very interesting and well worth further study. 
Although the genus Catenicellce comprises so many species, 
twenty-four at least being found on this coast, I was only able to 
find one alive. This was <7. formosa , a very lovely species, but 
like all true beauties, it seemed chary of displaying its charms. 
On one occasion I sat constantly for five hours vainly 
endeavouring to ascertain the number of its tentacles. There 
seemed to be more than twelve, probably sixteen; but during 
the whole of that time not one polyzoon would remain motionless 
