476 POLYZOA 



many important respects. T do not, however, accept the view, 

 maintained by some authors, that the Entoprocta and the Eeto- 

 procta are two separate classes which are not nearly related. 



The base from which the whole set of tentacles springs is 

 known as the " lophophore." 1 In the Entoprocta (Fig. 236, 1) 

 the lophophore is circular ; the mouth is situated near the 

 margin of the area surrounded by the tentacles ; and the anus 

 is found within the circlet, near the end opposite to the 

 mouth. 



In (2) and (3), representing the Ectoprocta, the anus is 

 outside the series of tentacles. In the majority of cases, includ- 

 ing all the marine Ectoprocta and one or two of the fresh-water 



O 



_jc ) i : 9 1 % 



Fig. 236. Ground-plan of the lophophore in (1) Entoprocta, (2) Gymnolaemata, (3) 

 Phylactolaemata : a, anus ; ep, epistome ; m, mouth. The tentacles are repre- 

 sented by shaded circles. 



forms, the lophophore is circular (2), the mouth occurring at the 

 centre of the circle, and not being provided with a lip. These 

 forms of Ectoprocta constitute the Order Gymnolaemata, 2 the 

 dominant group of the Polyzoa in respect of number of genera 

 and species. The remaining Ectoprocta belong to the exclusively 

 fresh-water Order Phylactolaemata, 3 in which the mouth is 

 protected by an overhanging lip or " epistome " ; the ground- 

 plan of the tentacles is, except in Fredericella, horse-shoe shaped 

 (Fig. 236, 3), and the tentacles themselves are usually much 

 more numerous than in the other cases. 



The general characters of these divisions will be more easily 

 understood by referring to the figures given of living representa- 

 tives of the groups. The Entoprocta are illustrated by Figs. 

 243-245; the Gymnolaemata by Figs. 238, 240; and the 

 Phylactolaemata by Figs. 247, 248. 



1 \6<pos, crest or tuft. 2 yv/xvos, naked ; Xai/xos, throat. 3 (pvXdaau, I guard. 



