642 THE AMERICAN NATURALIST. [Vor. XXXIV. 
The basal joint of the antenna is articulated with the front 
by a transparent flexible membrane, the antennary fossa, and 
allows of the free play of the antenna. On the inner side of 
and above the antennary fossa there is a peculiar membranous 
area of paler color —the fenestra. According to Sedgwick 
this fenestra is replaced by an ocellus in some cockroaches 
(the males of Corydia and Heterogamia) If so, we must 
regard this fenestra as a rudimentary ocellus. 
A little below the fenestra, and in the broad, flattened 
region of the front, there is another peculiar spot marked 4, 
which seems to have escaped the notice of all observers. This 
spot is, however, more prominent than the fenestra, and it 
looks like one of the originally paired ocelli, which afterward 
migrated toward the median line and fused together to form a 
middle ocellus in other insects. 
There often occur some perplexing dark spots in the head 
of the insects, surrounding their ocelli, but they vary a great 
deal in size and number as well as in shape and position. But 
in the cockroach these four spots are always present through- 
out all the species I have examined. Two of them are regu 
larly situated in the vertex, near its cephalic margin (sometimes 
they are situated on the boundary line between the vertex and 
