1 86 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 vihracula 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. ENTOPROOTA. 



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 Loxosoma 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. 



