EXPERIMENTS IN STIMULATION. 61 



passes were provided with india-rubber sliders, so 

 that by placing these under the Medusa, the latter 

 might be kept at any elevation in the water which 

 might be desired. The manubrium and lithocysts 

 were now removed, and also a segment of the um- 

 brella. A light straw was then forced through the 

 gelatinous substance of the umbrella in a radial 

 direction, and close to the gap caused by the missing 

 segment. The other, or free, end of this straw was 

 firmly joined to a capillary glass rod, which was suit- 

 ably bent to avoid contact with the rim of the basin, 

 and also to write on the smoked cylinder. If the 

 straw was not itself sufficient to support the weight 

 of the capillary rod, a small cross-piece of cork 

 might easily be tied to it, so as to add to the 

 flotation power. A part of the excitable tissue 

 was now raised above the surface of the water by 

 means of a disk of cork placed beneath it, and on 

 the part of the tissue thus raised there were placed 

 a pair of platinum electrodes. These electrodes 

 proceeded from an electro-magnetic apparatus, which 

 was arranged in such a way that every time the 

 current in it was opened or closed, it gave an 

 induction shock and moved a lever at the same 

 instant of time. This lever was therefore placed 

 upon the cylinder immediately above the capillary 

 glass-writer which proceeded from the Medusa 

 care being taken to place the two writers in the 

 same line, parallel to the axis of the cylinder. 

 Such being the arrangement, the cylinder was 

 rotated, and thus two parallel lines were marked 

 upon it by the two writers. If the current was 



