366 SEA-SIDE STUDIES. 



from some internal impulse, and not from an obvious 

 external cause, we cannot help attributing it to "the will." 

 No one seeuig a bu-d snap at a fly with its beak, could 

 doubt that the movement was voluntary ; but if the bird's 

 head were cut off, and thie beak continued to snap, would 

 not this throw a serious doubt on the voluntary nature of 

 the former action ? Yet this is what occurs with the curious 

 avicidariuni, or " bird's-head process " of the Corkscrew 

 Coralline : an animal doubtless familiar to many readers, 

 some of whom have mistaken it for a Polype, it being indis- 

 tinguishable from a Polype by the naked eye (Plate VII., 

 fig. 4), although the microscope, revealing its internal struc- 

 ture, shows it to be a Polyzoon. The stem is twisted into 

 a corkscrew shape, sufficiently remarkable to attract atten- 

 tion in rock-pools, or in tanks. On examining it atten- 

 tively, it is generally seen to be furnished with a number of 

 processes resembling vulture-heads — one beneath each cup — 

 having two mandibles, one fixed, the other movable by 

 means of two sets of muscular fibres, visible within the 

 head ; and these mandibles keep up an incessant snapping, 

 which occasionally entraps some worm, or minute Crus- 

 tacea, in an inexorable grasp. Very interesting it is to 

 watch these birds' heads snapping with vague vigour, wliile 

 above them the animals, to which they can scarcely be said 

 to belong, are protruding from their cups ; for, be it noted, 

 the bird's head does not form part of the animal, but issues 

 from the stem on which the colony of animals abides ; as if 

 a gentleman residing in the parlour kept a watch-dog chained 

 to liis area gate. The position of this " process " has natur- 



