PROBABLE OFFICE OF THE " BIRD^S-HEADS." 439 



that they are not connected with the polyps, because 

 they are often found lively and active on the sides of 

 cells wherein there are none. 



There is something very comical in the energy and 

 earnestness with which the tiny jaws open and close, 

 and throw themselves about ; no cause being apparent 

 in general for the outrageous gapings and eccentric 

 jerks in which they indulge. 



While watching on one occasion a piece of Cellu- 

 laria avicularis under the microscope, the Rev. T. 

 Hincks observed a worm pass over it and among its 

 branches. It was almost immediately firmly grasped 

 by one of the " Bird's-heads," 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 meanwhile kept fast hold, and soon two 

 others caught the unfortunate creature at different 

 points of its body. Thus it was held until 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. At the end of the contest the 

 worm seemed exhausted by its struggles, and scarcely 

 stirred, the beaks remaining firm and motionless. 

 These strange police-officers, according to Mr. Hincks, 

 were very systematic in their operations, and in cap- 

 turing the intruder seemed to be discharging a very 

 ordinary function ; so that he thinks there can be 

 little doubt that it is the office of these organs to 

 defend the Bryozoon from enemies, and to arrest 

 creatures or substances which might injure or annoy 



