THE POLYZCLE. 143 



individuals, similar to the social republics of the polyps. 

 But in spite of this apparent resemblance, the flustrse have a 

 far more developed organisation ; for besides the rudiments of 

 a nervous system, which directs the independent movements of 

 each individual, and establishes by connecting filaments the 

 unity of the colony, they possess a very complicated muscular 

 apparatus, a complete digestive canal, and when they draw back 

 their tentacles, they are able to close their little cells 

 a kind of moveable lid, which no doubt affords them, security 

 against a host of microscopical foes. When fresh, the whole 

 structure exhales an agreeable acid odour, somewhat like that 

 of the lemon-scented verbena or geranium, but less pure. 



Besides the flustra?, the sea contains a great variety of allied 

 genera, some erected like them on short stalks (cellulariaB), while 

 others spread in concentric layers over sea-weeds or shells (lepra- 

 Iia3), and though appearing to the naked eye as rude and 

 unsightly scurfs, exhibit, when magnified, a wonderful diversity 

 and elegance of form. Other genera are tubular (tubuliporas), 

 others spongy (cellepora?). Generally the cellular extension is 

 unbroken, but sometimes (reteporaB) the leaf-like expansion is 

 pierced like net-work. Such is the exuberance of fancy dis- 

 played in the formation of the group of the polyzoa, as this 

 humblest subdivision of the great series of molluscous animals 

 has been named. 



But a closer inspection reveals still greater wonders to the 

 marine microscopist, for most of the polyzoa, and particularly 

 the cellularise, possess very remarkable appendages or processes, 

 presenting the most striking resemblance to the head of a bird. 

 Each of these processes or <avicularia3 ' has two ( mandibles,' of 

 which one is fixed like the upper jaw of a bird, the other move- 

 able like its lower jaw ; the latter is opened and closed by two 

 ?.ets of muscles, which are seen in the interior of the head, and 

 between them is a peculiar body, furnished with a pencil of 

 bristles which is probably a tactile organ, being brought forwards 

 when the mouth is open, so that the bristles project beyond 

 it, and being drawn back when the mandible closes. During 

 the life of the polyzoon, these tiny ( vulture-heads,' which are 

 either sessile or pedunculated, keep up a continual movement ; 

 and it is most amusing to see them see-sawing, and snapping 

 and opening their jaws, and then sometimes in their incessant 



