STRUCTURE OF ALCYONIAN POLYPES. 50.") 



radiating from its walls. Instead of being closed at its lower 



extremity, however, it opens into the canals which ramify 



through the fleshy mass, and which thus connect all the Polypes 



into one system. This opening is 



surrounded by a circular muscle, or 



sphincter, by the action of which it 



may be expanded or entirely closed. 



The chambers which surround the 



stomach correspond in number with 



the tentacula ; and these are hollow, 



opening below into the chambers 



(as in the Actinia), whilst they 



have a small orifice at their ex- 4 



tremity. The chambers are con-" 



tinuous at their lower part with ria.-i5.-ALCYONiAxpoi.YrK. 



the ramifying canals just mentioned ; 



and the membranous folds which support the stomach do not 



cease at its lower extremity, but are prolonged downwards as 



plaits of the lining of these canals, until they gradually disappear. 



1151. The ova or germs are developed in the substance of 

 the membranous folds, or from the lining of the canal. They 

 grow like seeds in a seed-vessel ; at first appearing as little pro- 

 tuberances from the plane surface ; then acquiring a distinct 

 globular form, and remaining attached by a little stalk; and 

 finally, being liberated by the separation of this pedicle. They 

 then make their way outwards, by passing into the stomach 

 through its lower aperture ; and finally escape by the mouth. 

 Like the gemmules of other Polypes, they consist in this state 

 of a membranous bag including fluid ; and they are covered with 

 cilia, by the action of which they move freely through the water 

 for some time before fixing themselves, though not with the same 

 rapidity as the ova of some other Polypes. They are usually 

 coloured with great vividness ; and, during their motions, they 

 often contract themselves and alter their form. 



1152. Very little is known of the general habits of these 

 Polypes ; but they probably differ but little from those of the 

 groups already described. We may pass on, therefore, to con- 



