March, 1834. 



COMPOUND ANIMALS. 



259 



moveable organs, like those of Flustra avicularia (found 

 in the European seas), attached to their cells. The organ, in 

 the greater number of cases, very closely resembles the head 

 of a vulture ; but the lower mandible can be opened much 

 wider, so as to form even a straight line with the upper. 

 The head itself possesses considerable powers of movement, 

 by means of a short neck. In one zoophyte the head itself 

 was fixed, but the lower jaw free : in another it was replaced 

 by a triangular hood, with a beautifully- fitted trap-door, 

 which evidently answered to the lower mandible. A species 

 of stony eschara had a structure somewhat similar. In the 

 greater number of species, each shell was provided with one 

 head, but in others each had two. 



The young cells at the end of the branches necessarily 

 contained quite immature polypi, yet the vulture-heads 

 attached to them, though small, were in every respect per- 

 fect. When the polypus was removed by a needle from any 

 of the cells, these organs did not appear in the least 

 affected. When one of the latter was cut off from a cell, the 

 lower mandible retained its power of opening and closing. 

 Perhaps the most singular part of their structure is, that 

 when there were more rows of cells than two, both in a Flustra 

 and an Eschara, the central cells were furnished with these 

 appendages, of only one-fourth the size of the lateral ones. 

 Their movements varied according to the species : — in some 

 I never saw the least motion ; while others, with the lower 

 mandible generally wide open, oscillated backwards and for- 

 wards at the rate of about five seconds each turn ; others 

 moved rapidly and by starts. When touched with a needle 

 the beak generally seized the point so firmly, that the whole 

 branch might be shaken. 



These bodies have no relation whatever with the production 

 of the gemmules. I could not trace any connexion between 

 them and the polypus. From their formation being com- 

 pleted before that of the latter; from the independence of 

 their movements ; from the difference of their size in dif- 

 ferent parts of the branch ; I have little doubt that in their 



s 2 



