186 ZOOLOGY 
parrot’s beak. The two halves are constantly opening and 
closing, and by their action in catching small worms, etc., they 
probably serve as defensive organs, as well as assist in keeping 
the colony clean. The smaller beak is believed to be a modified 
operculum, whilst the larger corresponds with a much modified 
zooecium. These structures exist in very various degrees of 
perfection, those of the genus Bugula being amongst the most 
specialised. 
The vibracula are long stiff processes which move up and 
down, and are possibly tactile in function, they are believed 
to be homologous with the lower beak of an avicularium. In 
one genus they move in unison, and thus the colony exhibits 
some degree of co-ordination. 
B. ENTOPROCTA. 
This group contains but few genera. The mouth and the 
anus are both surrounded by the lophophore, which is circular. 
The tentacles can be bent over the mouth, but the anterior end 
of the body cannot be retracted into the posterior half. The 
coelom is almost completely obliterated. A pair of nephridia 
are present. 
This group is chiefly founded on the structure of two com- 
paratively well-known marine genera, Loxosoma and Pedicellina. 
Loxosoma is unique amongst Polyzoa, inasmuch as it is not 
colonial; like most Polyzoa, it increases by budding, but the 
buds separate from the parent organism. Both the genera are 
stalked, in Pedicellina the stalk arises from a creeping stolon, 
and the calyces or the bodies of the individuals often drop off, 
and are replaced by the regeneration of new ones at the end of 
the stalks, a process apparently analogous to the formation of 
brown bodies in ectoproctous forms. In ZLoxosoma the stalk, 
which carries the calyx, is at least in the young condition pro- 
vided at its lower end with a foot-gland, by means of which it is 
usually attached to some marine animal. The paired nephridia 
of Loxosoma consist of ciliated intra-cellular ducts piercing 
a few large cells, and probably each beginning with a flame 
cell. The ducts open to the exterior between the ganglion 
and the oesophagus. 
