SEA-ANEMONES : THEIK WEAPONS. 869 



they maintain this posture. But more commonly, 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 the pterygia, are continued on the attenuated portion 

 of the ecthoreum, perhaps throughout its length. In Cor. 

 viridis and Car. Smithii, I have succeeded in tracing them 

 up a considerable distance. In the latter I saw the con- 

 tinuation 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 

 Sagartia, however, it is by far the rarer form, while in 

 Actinia and Anihea 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 cnida. 

 A fragment of its craspeda I have here ready for your 

 observation, prepared exactly like that of C. Smithii. The 

 figure of the cnidm is nearly that of a perfect oval, but a 

 little flattened in one aspect, about s^th. of an inch in the 

 longer, and y^th 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 (ecthoreum) of great length 

 and tenuity, coiled up in some instances with an approach 

 to regularity, but much more commonly in loose contor- 

 tions, like an end of thread rudely rolled into a bundle 

 with the fingers. 



The armour of this kind does not differ essentially 



B B 



