EXPERIMENTS IN STIMULATION. 51 
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 
