BIRD S HEAD PROCESSES. 



319 



eruptions, so as to justify their name derived from the hideous 

 leprosy of the East, but, when magnified, their cells, generally 

 disposed in regular concentric rows, exhibit a surprising 

 diversity and elegance of structure. Forty species are found 

 in the North Sea alone ; hence we may judge how great the 

 number of still unknown forms must be that spread their 

 microscopic traceries over the algae and shells of every zone. 



It would lead me too far were I minutely to describe the 

 Cellularise with their cells disposed in alternating rows on 

 narrow bifurcated branches ; the Tubulipores, with their mouths 

 at the termination of tubular cells without any movable 

 appendage or lip; the Bowerbankias and Lagunculas, with 

 their creeping stems and separate cells ; suffice it to say that a 

 wonderful exuberance of fancy displays itself in the structure 

 of the numerous varieties of the Polyzoa. 



But a closer inspection reveals still greater miracles to the 

 marine microscopist, for most genera, and chiefly the CellularisB, 

 possess very remarkable appendages, or processes, presenting the 

 most striking resemblance to the head of a bird. Each of these 

 or " avicula- 



rise," as they have been 

 named, has two "man- 

 dibles," of which one is 

 fixed like the upper jaw 

 of a bird, the other 

 movable like its lower 

 jaw ; the latter is opened 

 and closed by two sets of 

 muscles, which are seen 

 in the interior of the 

 head, and between them 

 is a peculiar body, fur- 

 nished with a pencil of 

 bristles, which is pro- 

 bably a tactile organ, 

 being brought forwards 

 when the mouth is open, 



4.V. ±4.1, V.™ (.lac -rvrn A. Portion of a CelMan&, magnified. 

 SO mat tne DriSUieS pro- B _ A B]Td>B Head P]. oce3 s, more highly magnified, 

 je<5t beyond it, and being and seen m the act of grasping another. 



drawn back when the mandible closes. During the life of the 



