xvii ANATOMY OF ENTOPROCTA 491 



A pair of ciliated excretory tubes open into the vestibule. 

 These are similar in structure to the " head-kidneys " of the 

 larvae of Polychaet worms, or to the excretory organs of adult 

 Kotifers. Flame-cells have been described by Davenport in 

 the stalk of Urnatella, but it is not known whether they are 

 connected with the excretory tubes of the calyx. The animals 

 are either hermaphrodite or have separate sexes, and the gener- 

 ative organs open by ducts of their own into the vestibule. 

 The nervous system consists of a ganglion placed between the 

 mouth and the anus, giving off a set of nerves, many of which 

 end in delicate tactile hairs placed on the tentacles or other 

 parts of the body. 1 



1 For a recent account of the Entoprocta, sec Ehlers, <! Zur Kenntniss d. Pedicel- 

 lineen," Abh. Ges. Gottingen, xxxvL 1890, No. iii. 



