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 algze and shells of every zone, 
It would lead me too far were I minutely to describe the 
Cellulariz 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 Cellularia, 
possess very remarkable appendages, or processes, presenting the 
most striking resemblance to the head of a bird. Each of these 
processes, or “ avicula- 
riz,” 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, 
A. Portion of a Cellulana, magnified. 
B 
so that the bristles Cee . A Bird’s Head Process, more highly magnified, 
ject beyond it, and being and seen in the act of grasping another. 
drawn back when the mandible closes. During the life of the 
