THE ACTIONS OF BRAINLESS CRAYFISHES. 111 
—n bit of metal, or wood, or paper, or one of the ani- 
mal’s own antennsze—is placed between the chele of the 
forceps, it is at once seized by them, and carried back- 
wards ; the chelate ambulatory limbs are at the same 
time advanced, the object seized is transferred to them, 
and they at once tuck it between the external maxilli- 
pedes, which, with the other jaws, begin vigorously to 
taasticate it. Sometimes the morsel is swallowed; 
sometimes it passes out between the anterior jaws, as i 
deglutition were difficult. It is very singular to observe 
that, if the morsel which is being conveyed to the mouth 
by one of the forceps is pulled back, the forceps and the 
chelate ambulatory limbs of the other side are at once 
brought forward to secure it. The movements of the 
limbs are, in short, adjusted to meet the increased 
resistance. 
All these phenomena cease at once, if the thoracic 
ganglia are destroyed. It is in these, therefore, that the 
simple stimulus set up by the contact of a body with, for 
example, one of the forceps, is translated into all the sur- 
prisingly complex and accurately co-ordinated movements, 
which have been described. Thus the nervous system 
of the crayfish may be regarded as a system of co-ordi- 
nating mechanisms, each of which produces a certain 
action, or set of actions, on the receipt of an appropriate 
stimulus. 
When the crayfish comes into the world, it possesses 
in its neuro-muscular apparatus certain innate poten- 
