sea-anemones: their weapons. 371 



the M r hole had been run off. So exceedingly subtle are 

 the walls of the cnidce, that it was not until after many 

 observations that I detected them ; in an example from 

 T. crassicornis, which had discharged about half of the 

 wire, I could not see the slightest sign of armature on 

 the ecthoreum. So far as my investigations go, these 

 Spiral Cnidse are confined to the walls of the tentacles, 

 in which, however, they are the dominant form.* 



Such, then, are the form and armour of these organs. 

 But I have not yet done with them. The emission of 

 the wire, strange to say, is a process of distinct evolution, 

 or expansion from within, from beginning to end. The 

 ecthoreum is not a solid, but a tubular, prolongation of 

 the walls of the cnida, turned-in, in its first condition ,. 

 like the finger of a glove drawn inwards. Of this fact 

 you may convince yourself by a careful watching of the 

 phenomena before you. Many of the ecthorea from the 

 tangled cnidce now under your eye run out, not in a 

 direct line, but in a spiral direction. Select one of these, 

 and you w T ill perceive that each bend of the spire is 

 made, and stereotyped, so to speak, in succession, while 

 the tips go on lengthening ; the tip alone progresses, the 

 whole of the portion actually discharged remaining 

 perfectly fixed ; which could not be on any other 

 supposition than that of evolution. 



In the discharge of the chambered kind (to revert to 

 those which we were just now examining) we saw the 

 ventricose basal part first appear ; the lower barbs flew 

 out before the upper ones, and all were fully expanded 

 before the attenuated portion began to lengthen. This, 

 again, is consistent only with the fact of the evolution of 

 the whole. On several occasions of observation on the 

 chambered cnidce of C. Smithii, I have actually seen the 

 unevolved portion of the ecthoreum running out through 



* These details, with many others, are given in my Hist, of Brit. 

 Sea-anemones and Corals, Introd., xxii — xl. 



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