SEA- ANEMONES : THEIE WEAPONS. 423 



sometimes thej maintain tliis posture. But more com- 

 monly, either in an instant, or slowly and gradually, 

 they assume a reverted dij^ection. 



" From some delicate observations made with a veiy 

 good light, I have reason to conclude that the strebla^ 

 and even t\\Q pterygia, are continued on the attenuated 

 portion of the ecthorcBwn, perhaps throughout its length. 

 In Cor. viridis and Cyathina Smithii^ I have suc- 

 ceeded in tracing them up a considerable distance. In 

 the latter I saw the continuation of all these bands, 

 with their bristles, but what was strange, the angle of 

 inclination had become nearly twice as acute as before, 

 being only 22° from the axis. The appearance of the 

 attenuate portion, as also of the base of the ventricose 

 part, is exactly that of a three-sided wire, twisted on 

 itself; the barbs projecting from the angles. 



" The next form of these oro-ans is the Tangled 

 Cnida. This form is very generally distributed, and 

 is mingled with the former in the various tissues. In 

 the genus Sagartia^ however, it is by far the rarer form, 

 while in Actinia and Anthca it seems to be the only 

 one. 



" The pretty little Corynactis viridis is the best 

 species that I am acquainted with for studj'ing this 

 kind of cnidcB. [A fragment of its craspeda I have 

 liere ready for your observation, prepared exactly like 

 that of C. Sinithii.'] Their figure is near that of a per- 

 fect oval, but a little flattened in one asj^ect, about 

 ji^tli of an inch in the longer, and -^f otli in the shorter 

 diameter. Their size, therefore, makes them peculiarly 

 suitable for observations on the structure and functions 

 of these curious organs. Within the cavity lies a 

 thread {ecthorceum) of great length and tenuity, coiled 



