SEA-ANEMONES I THEIR WEAPONS. 369 



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 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 

 Sagartia, 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 cnida- . 

 A fragment of its craspeda I have here ready for your 

 observation, prepared exactly like that of C. Smithii. 

 The figure of the cnidce is nearly that of a perfect oval, 

 but a little flattened in one aspect, about -^o^h °^ 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 contortions, like an end of 

 thread rudely rolled into a bundle with the fingers. 



The armour of this kind does not differ essentially 



2 B 



