SECTION OF COVERED-EYED MEDUSA. 85 



on the contraction-waves beyond the areas of 

 previous blocking. In such instances, of course, v^^e 

 should expect to find wliat I always observed to be 

 the case, viz. that the first contraction- wave which 

 passes the barrier is only very feeble, the next 

 stronger, the next still stronger, and so on, accord- 

 ing as the new passage becomes more and more per- 

 meable by use, until at last the contract ion- waves 

 pour over the original barrier without any per- 

 ceptible diminution of their force. In some cases, 

 by exploring with graduated stimuli and needle- 

 point terminals, I was able to ascertain the precise 

 line through which this eruption of stimulating 

 influence had taken place." 



I have now to state the effect upon this hypo- 

 thesis which in my opinion has been produced by 

 the histological proof that the plexus in question is 

 composed of fully differentiated nerves. Briefly, 

 then, I think that the hypothesis still holds to the 

 extent of being the only one available whereby to 

 explain the facts ; but there is this great difference, 

 viz. that the hypothesis need not now be applied 

 to the genesis of nerve-tissue out of comparatively 

 undifferentiated contractile tissue, but rather to the 

 increasing of the functional activity of already well- 

 differentiated nerve-tissue. In other words, we 

 have not now to suppose that nerve-tissue is 

 formed de novo in the region of blocking ; but, in my 

 opinion, we still have to suppose that the nerve- 

 libres which were already there have their func- 

 tional capabilities so far improved by the greater 

 demand imposed upon them, that whereas at first 



