112 JELLY-FISH, STAR-FLSH, AND SEA-URCHINS. 



I shall now proceed to consider the nature of the 

 nervous connections between the nectocalj^x and 

 manubrium of this Medusa. 



Bearing in mind that in an unmutilated Tiaropsis 

 indicans the manubrium invariably localizes with 

 the utmost precision any minute point of irrita- 

 tion situated in the bell, the significance of the 

 following facts is unmistakable, viz. that when a 

 cut is introduced between the base of the manu- 

 brium and the point of irritation in the bell, the 

 localizing power of the former, as regards that point 

 in the latter, is wholly destroyed. For instance, if 

 such a cut as that represented at a (see Fig. 22) be 

 made in the nectocalyx of this Medusa, the manu- 

 brium will no longer be able to localize the seat of 

 a stimulus applied below that cut, as, for instance, 

 at h. Now, having tried this experiment a number 

 of times, and having always obtained the same 

 result, I conclude that the nervous connections be- 

 tween the nectocalyx and the manubrium, which 

 render possible the localizing action of the latter, 

 are connections the functions of which are intensely 

 sjDecialized, and the distribution of which is radial. 



So far, then, we have highly satisfactory evidence 

 of tissue-tracts performing the function of afferent 

 nerves. But another point of interest here arises. 

 Although, in the experiment just described, the 



case bending over in whatever direction it was needful for it to 

 bend, in order to approach the seat of stimulation. This shows 

 that the analogue of ganglionic function must here be situated in 

 at least more than one part of a tentacle ; and I think it is not 

 improbable that, if trials were expressly made, this function would 

 be found to be diffused throughout the whole tentacle. 



