. INTRODUCTION. XXXIX 



with impunity. And I have elsewhere* recorded an in- 

 stance, in which a little fish, swimming about in health and 

 vigour, died in a few minutes with great agony, through 

 the momentary contact of its lip with one of the emitted 

 acontia of Sagartia parasitica. It is worthy of observation, 

 that, in this case, the fish carried away a portion of the 

 acontium sticking to its lip ; the force with which it ad- 

 hered being so great, that the integrity of the tissues yielded 

 first. The Acontium severed, rather than let go its hold.\ 



Now, in the experiments which I have detailed above, 

 we have seen that this adhesion is effected by the actual 

 impenetration of the foreign body, by a multitude of the 

 ecthorcea, whose barbs resist withdrawal. So that we can 

 with certainty associate the sudden and violent death of 

 the little fish with the intromission of barbed ecthorcea. 



I have instituted some experiments with a view to try 

 whether acid or alkaline properties could be detected in the 

 (presumed) fluid which is discharged. First with a solu- 

 tion of indigo, and afterwards with the expressed juice of 

 violets, I occupied the plate of the compressorium ; and in 

 the flattened drop made the cnida in the acontium of S. 

 parasitica to emit. In the case of the indigo, the colouring 

 matter remained in the form of masses, but the juice of 

 violets affords an apparently homogeneous fluid, even when 

 reduced by pressure to an excessively thin film. I could 

 not detect, even with the most careful scrutiny, the slightest 

 tinge of discoloration of the blue fluid, — not the most 

 delicate shade of red or green — along the side of the 

 emitted ecthortea, nor in the vicinity of the cnidce. And 



* " The Aquarium," ed. 1. p. 115. 



+ Dr. Waller has recently recorded an interesting experiment which he 

 made with Act. viesembryanthemum. He allowed its tentacles to touch 

 the tip of his tongue. " The result was such as to satisfy the most scep- 

 tical respecting the offensive weapons with which it is furnished. The 

 animal seized the organ most vigorously,, and was detached from it with 

 some difficulty after the lapse of about a minute. Immediately a pungent 

 acrid pain commenced, which continued to increase for some minutes, 

 until it became extremely distressing. The point attacked felt inflamed 

 and much swollen, although to the eye no change in the part could be 

 detected. These symptoms continued unabated for about an hour, and a 

 slight temporary relief was only obtained by immersing the tongue in cold 

 or warm water. After this period the symptoms gradually abated, and 

 about four hours later, they had entirely disappeared. A day or two after, 

 a very minute ulceration was perceived over the apex of the tongue, which 

 disappeared after being touched with nitrate of silver."— (Proc. Roy. Soc. 

 April 14, 1859.) 



