SECTION OF NAKED-EYED MEDUSJE. Ill 



ab least, to the size which is compatible with con- 

 ducting these experiments — is independently en- 

 dowed with the capacity of very precisely localizing 

 a point of irritation which is seated either in its 

 own substance or in tliat of the bell. 



We have here, then, a curious fact, and one 

 which it will be well to bear in mind during our 

 subsequent endeavours to frame some sort of a con- 

 ception regarding the nature of these primitive 

 nervous tissues. The localizing function, which is 

 so very efficiently performed by the manubrium of 

 this Medusa, and which if anything resembling it 

 occurred in the higher animals would certainly 

 have definite ganglionic centres for its structural 

 co-relative, is here shared equally by every part of 

 the exceedingly tenuous contractile tissue that 

 forms the outer surface of the organ. I am not 

 aware that such a diffusion of ganglionic function 

 has as j^et been actually proved to occur in the 

 animal kingdom, but I can scarcely doubt that 

 future investigation will show such a state of things 

 to be of common occurrence among the lower 

 members of that kingdom.* 



* The only case I know which rests on direct observation, and 

 which is at all parallel to the one above described, is the case of 

 the tentacles of Drosera. Mr. Darwin fonnd, when he cut ofE the 

 apical gland of one of these tentacles, together with a small por- 

 tion of the apex, that the tentacle thus mutilated would no longer 

 respond to stimuli applied directly to itself. Thus far the case 

 dillers from that of the manubrium of Tiaropsis indicans, and, in 

 respect of localization of co-ordinating function, resembles that 

 of ganglionic action. But Mr. Darwin also found that such a 

 *' headless tentacle " continued to be influenced by stimuli applied 

 to the glands of neighbouring tentacles — the headless one in that 



