18 Bulletin Wisconsin Natural History Society. [Vol. 10, Nos. 1 & 2. 
the two sides of the body. In forms with positive phototaxis it 
was found that blackening over one eye caused the amphipod to 
perforin circus movements toward the normal side. In negatively 
phototactic species it was found that the same treatment caused 
circus movements in the reverse direction. It is probable therefore 
that impulses received by the eyes cross in the central nervous 
system and becomes carried to the appendages on the opposite side 
of the body causing them to act with greater vigor, thus bringing 
the animal into a position of orientation. This supposition led 
to the experiment of cutting the brain lengthwise through the 
center in several species of arthropods and it was found that, 
although sensitiveness to light could be shown to remain, all power 
of orientation to light was entirely destroyed. 
It will be of interest in this connection to consider the light 
reactions of a somewhat more highly organized arthropod; the 
water scorpion Ranatra. This insect lives near the banks of ponds 
and streams with the tip of its long breathing tube at the surface 
of the water and its raptorial fore legs held in a position for rapidly 
seizing any small passing creature which may be utilized for food. 
When Ranatra is taken out of the water it generally feigns death, 
assuming a perfectly rigid attitude which it retains through all 
sorts of maltreatment, even suffering its legs to be cut off or its 
body cut in pieces without betraying any signs of animation. By 
moving a light over the motionless insect it may gradually be 
brought out of its feint. The first noticeable signs of awakening 
are very slight movements of the head in response to the move¬ 
ments of the light. When the light is passed to one side of the 
body the head is rolled over ever so little toward that side. Move 
the light to the other side and the head tilts over slightly in that 
direction. Place the light in front of the body and the head bows 
down, in front, and when the light is behind the insect the front of 
the head is pointed slightly upward. These movements occur with 
perfect regularity in response to the movements of the light, and 
gradually increase in vigor and extent. After following the move¬ 
ments of the light with these definite movements of the head the 
insect slowly and awkardly raises itself up and begins to follow 
the light with equally definite swaying movements of the body. 
If the light is to one side the legs on that side are flexed and the 
opposite legs extended. Passing the light over the body causes 
