348 ZOOLOGY sect. 



Sul-order c. — Ctenostomata. 



Gymnoluemata with chitinous or gelatinous zocecia provided with 

 a series of tooth-like processes closing the aperture Avhen the 

 tentacles are retracted. 



Including Alcyonidium, Serialaria, Paludicella. 



Order 2. — Phylactol^emata. 



Fresh- water Ectoprocta with horse-shoe-shaped lophophore and 

 with an epistome. 



Including Cristatella, Plumatella, Fredericella. 



Sub-Class II.— Endoprocta. 



Colonial or solitary Polyzoa multiplying by the formation of 

 buds, which in Loxosoma soon become separated off, while in 

 Pedicellina they remain connected together by a creeping stolon. 

 The anus, as well as the mouth, is internal to the lophophore. 

 The introvert is slightly or not at all developed. A pair of ciliated 

 nephridial tubes are present. 



Systematic position of the Example. 



Bugula avicularia is an example of the sub -order Cheilostomata 

 of the Gymnolsemata. It is a member of the family Bicellariidse, 

 which is characterised by the erect plant-like colony, with narrow 

 compressed branches, and attached by root-like fibres; by the 

 avicularia, when present, being stalked and bird's-head shaped ; and 

 by the wide oblique apertures of the zocecia all facing in the same 

 direction. Bugula differs from the other genera of the family in 

 the arrangement of the zocecia in double or multiple rows, in their 

 close union, and in the avicularia, when present, being on the side 

 on which the mouth is situated. The various species differ in the 

 exact shape of the zocecia and of the avicularia. 



3. General Organisation. 



Sub-Class I. — Ectoprocta. 



The Ectoprocta and the Endoprocta differ so considerably from 

 one another that it is advantageous to deal with them separately. 

 The Ectoprocta are all colonial — the colonies being capable, in 

 most cases, like the colonies of hydroid zoophytes, of increasing in 

 size to an ' apparently indefinite extent by continuous budding. 

 The thickened cuticle which forms the support of the colony is 

 sometimes gelatinous, sometimes chitinous, sometimes chitinous 

 with sand-grains affixed, sometimes calcareous. The form of the 



