356 Wisconsin Academy of Sciences , Arts and Letters. 
ver was, after preparing the eye, to determine the number of 
rods covered by an object of given size at various distances. 
He concludes that the four pairs of eyes receive four pairs of 
different sized images ; that the images on the anterior middle 
eyes, which are much the richest in rods, are by far the most 
perfect, those on the anterior laterals next, on the posterior side 
eyes next, and on the middle side eyes least; that probably vi¬ 
sion is slightly distorted for all things that lie outside the axis 
of the eye, but that the spider may, nevertheless, form a true 
idea of objects, first because the distortion in each eye of a 
pair is corrected by the opposite eye of the same pair, and sec¬ 
ond because the retina is not a plane, but is of a very compli¬ 
cated form, differing in different eyes and for different species. 
He finds that Phidippus tripunctatus coming within 30 c. m. 
of another spider, would receive a sharp image, covering a suf¬ 
ficient number of rods to ensure recognition of species and sex. 
This J confirms our observations, in which we found that Attidse 
recognized each other easily at a distance of twelve inches. To 
make sure that sight was the sense involved in this recognition 
we several times covered the eyes of the males with paraffin, 
after which they seemed unconscious of the presence of the fe¬ 
males. We also took pale-colored females which were being 
ardently courted by the males and painted them bright blue, 
after which they to a great extent lost their charm, being en¬ 
tirely neglected for a time, although some of the males after¬ 
wards became reconciled to the change in their appearance and 
again danced before them. These experiments, however, dealt 
with abnormal conditions, and we consider them much less im¬ 
portant than the fact, which we constantly observed, that the 
females, whose presence in front always threw the males into a 
fever of excitement, could approach them closely without being 
noticed so long as they were behind and out of sight—or at least 
in sight only of the relatively imperfect eyes of the third pair. 
It seems plain, then, that the males and females must see each 
other before their interest is aroused. In the case of the female 
this interest is manifested only in the mating season. 
It being settled that the females can see the males it becomes 
