1876 



MEDUSiE 



27 



a similar progressive increase is observable on ap- 

 proaching one of the radial canals, and is greatest 

 when electrodes are placed on one of these. (I may 

 observe that however neat a person's fingers may be 

 it would be simply impossible to conduct these 

 and other obser\'ations of the same nature without 

 a mechanical stage. The electrodes must be needle- 

 points passed through cords, the latter being sup- 

 ported by a copper wire fixed to the stage, and 

 therefore moveable with it ; and I defy anybody to 

 get the electrodes into the 

 field, and at the same 

 time upon the marginal 

 canal, unless they all 

 move together.) 



Sarsia stands an 

 astonishing amount of 

 section without losing 

 nervous conductibihty. 

 For instance, the whole 

 organism may be cut 

 into a three -turned spiral, 



and on irritating the end, the whole contracts ; 

 yet a moment's thought will show how trying this 

 mode of section is to nervous connections. As the 

 animal may be cut, as in the following diagram, 

 which represents the whole organism in projection — 

 the dotted lines being the canals, and the thick ones 

 the cuts — on now irritating any part of the animal, 

 the whole contracts, but the co-ordination power is 

 lost, both iu spontaneous contraction and for those in 

 response to stimuli. 



Fig. 



