OTHER UNSEGMENTED WORMS 



191 



support for the colony. Sometimes lime is added. Because of their 

 superficial resemblance to corals such forms are known as coralline 

 bryozoans. A mouth at the outer end is sur- 

 rounded by a crown of cihated tentacles termed 

 the lophophore, which exhibits the form of a horse- 

 shoe when it is expanded. The U-shaped alimentary 

 canal opens by an anus situated near the mouth 

 and either within or without the lophophore. 

 There are neither circulatory nor excretory organs. 

 The nervous system consists of a central ganglion 

 between the mouth and anus. Reproduction is both 

 sexual and asexual, the latter taking place by bud- 

 ding. These animals are either monecious or 

 diecious. The eggs are fertilized in the coelom and is "somewhat similar. 

 develop in a modified portion of the body cavity ^^^l^^^ j^^l^^lHistir^" 

 called an ooecium which serves as a brood pouch, by the courtesy of The 

 The larva is in many respects like a trochophore. Macmiiian Company.) 



•^ ^ Natural size. 



Certain species produce nidividuals of a peculiar 

 type called avicularia. These are highly modified forms possessing a pair 

 of strong jaws, which probably are used in defense. 



Fig. 102.— a colony 

 of marine bryozoans, 

 Bugula turbinata Alder. 

 A British species; an 

 American species, 

 Bugula turrita (Desor), 



Lophophore 



Av/cc//arr/u/rr, 



jaws 

 c/osed 



Musc/e -^o 

 boofy wa/J 



Ovary 

 Sto/r7ach 

 Furicu/us 



Ooec/u/7^ 



Pharynx 



Anas 



EsophagfU-ff 



Avicu/anum, 

 Jaws oper 



/vfasc/e to 

 boc/y wa// 



S-f-omach 

 Ovary 

 Funr'cc//(js 

 Testes 



Fig. 103. — Bugula avicularia (Pallas), a European species. Two zooids are shown, the 

 one at the left entire, that at the right turned 90 degrees to the first and sectioned. Two 

 avicularia are shown, one with the jaws closed and the other with them open. An ooecium 

 is also included in the figure. {Redrawn from Parker and Haswell, "Text-book of Zoology," 

 somewhat modified.) Much magnified. 



