SEA-AKEMONES : THEDB WEAPONS. 423 



sometimes they maintain this postm-e. Bat more com- 

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

 they assume a reverted direction. 



" From some delicate observations made with a very 

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

 and even Xke pterygia, are continued on the attenuated 

 portion of the ecthoroBum, perhaps throughout its length. 

 In Ocn\ viridis and CyatJiina 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 organs is the Tangled 

 Cnida. This form is very generally distributed, and 

 is mingled with the former in the various tissues. In 

 the genus SagarUa, however, it is by far the rarer form, 

 while in Actinia and Anthea it seems to be the only 

 one. 



" The pretty little Corynactis viridis is the best 

 species that I am acquainted with for studying this 

 kind of cnid'cB. [A fragment of its oraspeda I have 

 here ready for your observation, prepared exactly like 

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

 fect oval, but a little flattened in one aspect, about 

 ji^th of an inch in the longer, and ^ioth 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 {ecthoromm) of great length and tenuity, coiled 



