244 ZOOPHYTES. 



Perhaps the Avicularium may be ultimately found a generic charac- 

 ter. In as far as I know, it belongs chiefly, if not exclusively, to the genus 

 we have left, as instituted by later naturalists, the Cellularia, and hence 

 connected with the ascidian hydrse. We find it on the ciliata, the fast i- 

 giafa, avicidaris, just described, and the Flustra Murrayana. All with 

 cells guarded by spinous processes. 



Much obscurity hangs over the true nature of the Avicularium. But it 

 is obviously of animal organization, and endowed with spontaneous motions. 



From its external position and utter dissimilarity to the rest of the pro- 

 duct where affixed, we should at first sight deem it a parasite ; nor can we 

 discover any immediate connection between it and the living tenant of the 

 zoophyte. 



The Avicularium is always seated on the outside and about the middle 

 of the cell. I have never seen it otherwise. Also, if the leaf of the 

 zoophyte be composed of a longitudinal series of parallel cells, it is borne 

 on each margin of the leaf, or on one margin only. 



This organization, presents the strongest resemblance, in extreme 

 miniature, to a bird's head, as denoted by its name ; nor is the comparison 

 much impaired even by powerful magnifiers. 



It then seems to consist of three distinct principal organs, first a 

 basis a, founded on, or incorporated with the cell ; next a head b, connect- 

 ed with the basis ; and, in the third place, a lower mandible c, demonstrat- 

 ing the most lively action. — Plate XLVI. figs. 12, 13, a, b, c. 



In quiescence, the whole is like the head of a bird with the bill closed. 

 In activity, the lower mandible opening, folds back with a very wide gape. 

 Another joint apparently connects the head with the basis, wherein the 

 neck moves as in a socket. The bill opens and closes frequently ; the 

 spectator would say, for the purpose of absorbing some extraneous matter, 

 too minute or too refined for detection by human sense. 



The motion is of two kinds, the whole avicidarium bending backwards 

 and forwards ; when the head sometimes reclines as far back in proportion 

 as seen of a bird reclining its head between its shoulders. The other motion 

 is merely the opening and closing of the lower mandible, widely gaping, 

 and continuing thus, but stationary, when the whole zoophyte has perished. 



