THREAD CAPSULES. U7 



thesis on their side, I have the accumulated aud overwlielm- 

 ing weight of experimental evidence. 



What are these "capsides," or "urticating cells?" The 

 uninstructed reader may be told that all the Polypes are 

 supposed to urticate, or sting, like nettles ; and the nettling 

 organs, or urticating cells, are supposed to be minute suboval 

 microscopic capsules, quite transparent, containing within 

 them threads coiled up, which, on pressure, dart out to many 

 times the length of the capsule, into which they never return. 

 This thread Agassiz likens to a lasso thrown by the Polype 

 to secure its prey. I mil not enter here into minute details 

 of structure, which would only confuse the reader, who, if 

 curious, will find all that is known, in the works of Mr 

 Gosse, or in the treatises of Owen, Siebold, and Rymer Jones. 

 Any one who has once seen these threads under the micro- 

 scope darting out with lightning-rapidity, especially if he 

 uses a high power, will at once admit that the hypothesis of 

 the "nettling" or "urtication'' being performed by these 

 threads is an hypothesis so obvious, an explanation so natu- 

 ral, that — it should be doubted. In all complex matters, we 

 should mistrust the obvious explanation ; I do not say that 

 we should disregard, or reject it, but mistrust it. When we 

 know, on the one hand, that the Jelly-fish stings, and when, 

 on the other hand, we know that it is furnished with numer- 

 ous capsules, in which are coiled threads, to be seen darting out 

 when pressed, the idea of connecting the stinging with these 

 threads is inevitable ; but this is not enough for Science : it 

 is only a preparatory guess, which proves nothing ; it may 

 be right, it may be wrong. I believe it is altogether wrong. 



