1 84 



COLLEGE ZOOLOGY 



a common marine genus which shows the principal characteristics 

 of the group. 



The soft parts constituting the polypide lie within the true 

 ccelomic cavity bounded by the body-wall or zooecium. The 

 mouth lies in the midst of a crown of ciliated tentacles (Fig. 124) 



called the lophophore, which serve to 

 draw food particles into the body. 

 The U-shaped alimentary canal con- 

 sists of a ciliated oesophagus (Oes), a 

 stomach (D), and* an intestine which 

 opens by means of an anus lying 

 just outside the lophophore. One 

 retractor muscle (R) serves to draw 

 the polypide into the zooecium. The 

 funiculus (F) is a strand of meso- 

 dermal tissue attached to the base 

 of the stomach. There are no circu- 

 latory nor excretory organs. 



Both an ovary and a testis are 

 present in each individual ; they 

 may be found attached to the fu- 

 niculus or the body-wall. The eggs 

 are probably fertilized in the coelom 

 and then develop in a modified 

 portion of the zooecium called the 

 ocecium (Fig. 124, Ovz). The larvae 

 of some Bryozoa resemble a trocho- 

 phore (see p. 183). 

 Certain members of Bugula colonies are modified into struc- 

 tures called avicularicB (Fig. 124, Av). These have jaws which 

 probably protect the colony from the attacks of small organisms 

 and prevent the larvae of other animals from settling upon it. 



The Bryozoa may be separated into two distinct groups, the 

 Ectoprocta and Entoprocta. In the former the anus opens 

 outside of the lophophore, as in Bugula, and a ccelom is present. 



Oirz 



Fig. 124. — Bugula avicu- 

 laria, a Bryozoon. Av, avicu- 

 laria; D, alimentary canal; 

 F, funiculus; Oes, oesophagus; 

 Ovz, ovicells ; R, retractor 

 muscle; Te, tentacular crown. 

 (From Sedgwick, after v. Nord- 

 mann.) 



