160 



COMPAEATIVE ANATOMY. 



of the intestine is attached by laterally-directed fibrous chords to 

 the body-wall, as a rule, along the lateral lines. The hind-gut, 

 which arises from the mid-gut, is the shortest portion of the whole 

 canal, and is distinguished from the part in front of it by its 

 diminished breadth. 



In the Gordiacea the enteric canal is present in the entoparasitic 



larval stages only, and undergoes 

 retrogressive metamorphosis when 

 the sexual organs are developed. 

 In Gordius even the mouth dis- 

 appears. The organism, when it is 

 free, uses up the material which it 

 ingested by its enteron during the 

 earlier stages, in forming genera- 

 tive products, after it has given up 

 its parasitic habit, and the ingestion 

 of food. 



The enteric canal of the Cha> 

 tognathi resembles in many points 

 that of the Nemathelminthes, but 

 the enteron is connected to the 

 body-wall in a different way, namely 

 along its dorsal and ventral median 

 lines. Setiform hooks, arranged in 

 rows at the sides of the mouth, 

 serve as organs of prehension. 



§ 130. 



Although the digestive organs 

 of the Bryozoa are sharply marked 

 off into the three primitive di- 

 visions, they are exceedingly simple 

 in character. The mouth, which is 

 surrounded by the tentacles, or 

 placed in the centre of the lobate 

 process which carries them, is in 

 one division (Phyiactolasmata) over- 

 hung by a movable process — the 

 epistom. Thence it passes straight 

 back to an oesophageal portion 

 (Fig. 71, ve), which in some is 

 widened out or even converted into 

 a gizzard by the development of 

 denticular processes in one part of 

 The second portion is separated 

 from the fore-gut, which is invested with cilia, by a constriction 

 (v), and forms the mid-gut. It functions as a stomach, and forms a 

 cajcum, which generally descends some way down into the coclom. 



Fig. 71. Organisation of Bryozoa. .4 

 Paludicella Ehrenbergii. B Plu- 

 matella fruticosa. br Tentacular 

 branchiae. oe (Esophagus (fore-gut). 

 v Stomach, r Hind-gut. a Anus, i 

 Covering of the body (cell), x Posterior; 

 x' Anterior chord, at the insertion of 

 which into the body the generative 

 products are developed. t Testes. 

 o Ovary, m Retractor muscles of the 

 anterior portion of the cell. <mr Prin- 

 cipal retractor muscle (after Allman). 



it (Bowerbankia, Vesicularia) . 



