The Central Nervous System and Simple 
Reactions of a Rare Whip Scorpion 
WILLIAM A. HILTON 
A number of specimens of Trithyreus pentapeltis Cook were col- 
lected by the writer in the college park at Claremont. The only 
other record of any member of this family found in the United 
States is the early paper of Cook which describes this species from 
Palm Springs, California. At another time there will be published 
a description with figures of the general external anatomy of this 
interesting creature. Fig. 1 is partly from an outline drawing by 
Miss Margaret Moles. The general position of the nervous system 
is shown in the outline. So far as we could determine there were 
no sense organs but hairs. These for the most part were of the 
usual arthropod type, but there were several modifications of them 
as will be shown by Miss Moles at a later time. The hairs are 
most abundant under the body and are probably important organs 
for giving sensations from the surfaces where the animals run. The 
most remarkable hair sense organs are on the legs. The figure 
shows the position of these slender delicate structures, two on the 
first leg, one on the others. If an animal is approached by any object 
one of these hairs is apt to be touched, especially if attempts are 
made to seize the animal. At first it was almost impossible to be- 
lieve that the little creatures did not have eyes, they so well avoided 
all attempts to capture them with forceps. When approached by 
some object which probably touches one of the long hairs they run 
either backwards or forwards apparently with great accuracy de- 
termining the position of the approaching object. However their 
backward running is most marked and most remarkable. They run 
with great swiftness in a backward direction in some cases for sey- 
eral inches. I found little evidence of other sense organs than those 
of touch. They did not especially avoid strong odors, but after a 
rather long exposure to strong light or heat they sought refuge under 
some object. 
Although the chitin is thin in places the first attempts at serial 
sections through the whole body were not very successful. It was 
