SEA.-ANKMONES : TIIKIR WEATONS. 



417 



every ])art of their length, carry abroad tlieir f.ital 

 powers not tlie less surely than if each had been pro- 

 vided with a proper tube leading froni its free extrem- 

 ity to the nearest cincUsJ^ 



Curious as these contrivances arc, 

 there is yet much more to be told : 

 these are preparatory and ancillary, as 

 it were, to tlic elaborate mechanism by 

 which the ultimate object of the whole 

 provision is to be attained. The acon- 

 tiuin is but a reservior for the weapons 

 — a kind of quiver for the arrows; and 

 the cinclis is a provision for getting 

 them ready for action : we have not yet 

 looked at the arrows themselves. 



They occur under three principal 

 forms ; and for the investigation of these 

 we shall find it convenient to have re- 

 course to different species. 



The first and most generally distribu- 

 ted form is the Chambered Cnida, as it 

 is also the most elaborately organized. 

 I know of no species in which it can be 

 examined under so favourable circum- 

 stances as the pretty Madrepore {Cya- 

 thina Smithii) of. our south-western 

 coasts ; and as I have several specimens 

 of that species in my aquarium, subjects are at hand for 

 our investigation. The clear tentacles are, as you per- 

 ceive, crowned with opaque globular heads ; if I should 

 nip off one of these heads and flatten it by means of the 

 compressorium, you would see it literally composed of 



CNIDA OF MADBE- 

 rOKE. 



IS* 



