386 SEA-SIDE STUDIES. 



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 occa- 

 sionally entraps some worm, or minute Crustacea, in an 

 inexorable grasp. Very interesting it is to watch these 

 bird's-heads snapping with vague vigour, while 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 his area gate. The position of 

 this " process " has naturally led to the question, Is it 

 an organ, or a parasite ? The invariability of the 

 position, and there being never more than one bird's- 

 head to each animal, seem to point to its being an 

 organ ; but if so, what can be its function ? Mr Gosse 

 has suggested an ingenious answer : " Several observers 

 have noticed the seizure of small roving animals by 

 these pincer-like beaks ; and hence the conclusion is 

 pretty general that they are in some way connected with 

 the procm^ing of food. But it seems to have been for- 

 gotten, not only that these organs have no power of 

 passing the prey thus seized to the mouth, but also 

 that this latter is situated at the bottom of a funnel of 

 cUiated tentacles, and is calculated to receive only such 

 minute prey as is drawn within the ciliary vortex. I 

 venture to suggest a new explanation. The seizure of 

 a passing animal, and the holding it in the tenacious 



