ESCHARIDA. 335 
for the outrageous gapings and eccentric jerks in which 
they indulge. ‘They occur on several British species, as, 
for example, Mustra avicularis and Cellularia avicularis. 
“ While watching, on one occasion, a piece of the latter 
zoophyte through the microscope, a worm passed over it 
and among its branches. It was almost immediately firmly 
grasped by one of the avicularia, and forcibly detained. 
In a short time one end of it was seized by another, from 
which, however, by its violent contortions, it extricated 
itself, but not without injury. The first assailant, mean- 
while, kept fast hold, and soon two others caught the un- 
fortunate at different points of the body. Thus it was held 
securely pinioned; and all its efforts to disengage itself, 
which were most vigorous, proved unavailing. ‘The avicu- 
laria grasped the body of their victim most viciously, and 
nearly divided it. When I last observed the contest, the 
worm seemed exhausted by its struggles, and scarcely 
stirred; the deaks remaining firm and motionless. These 
strange police-officers were very systematic in their opera- 
tions, and, in capturing the intruder, seemed to be dis- 
charging a very ordinary function. 
“There can be little doubt, I think, that it is the office 
of these organs to defend the Bryozoon from its enemies. 
