1925] External Anatomy of Head and Abdomen of the Roach 209 
into an upper and lower region. The basal segments of the cercus 
are usually more annular, while the terminal ones are more cy- 
lindrical (Fig. 24). In the roach, the cercus migrates from the 
paraproct par (Figl 19) which originally bore it, and becomes 
secondarily associated with the epiproct ep. The cerciger eg or 
process of the epiproct ep bears the cercus in such cases, and the 
surcerciger seg forms a second pivotal point in certain of the move- 
ments of the cercus. 
In handling living roaches, one in made painfully aware of a 
most nauseating odor which clings to one’s fingers even after re- 
peated washing with soap and water. The fluid which produces 
this odor is probably secreted by the repugnatoria or scent glands 
labelled rep in Fig. 14. These repugnatoria are eversible glands 
located in the membrane between the fifth and sixth adbominal 
tergites, and are slightly nearer to the sixth than to the fifth 
tergite, so that they may possibly belong to the sixth abdominal 
segment. 
The gynomeres, or abdominal segments of the female which be- 
come modified to form the secondary sexual characters of the 
abdominal region, are the seventh, eighth and ninth uromeres. 
The sternite of the seventh abdominal segment is proudeed pos- 
teriorly to form the hypogynium hg of Fig. 14, which hides the 
oviositor, and forms the sides and floor of the gy natrium or 
genital chamber of the female, which receives the parts of the 
male in copula, and also forms a genital pouch for carrying the 
ootheca or egg-case which is carried protruding from the end of the 
abdomen, for a time, before it is deposited. Like the other ab- 
dominal sternites, the hypogynium hg of Fig. 14, has an anterior 
region as and a posterior region eus demarked by a transternal 
suture or ridge; but in addition to these typical divisions of the 
sterum, the seventh sternite has a backward projecting struc- 
ture gv, which is divided into two gynovalvae or pseudo-valves 
gv of Figs. 14, 15, and 16 in the American roach and certain of 
its allies. The gynovalvular membrane, as shown in Fig. 16, 
extends between these pseudovalves and upward on each side to 
the flanges of the paraprocts, to form a pouch for carrying and 
protecting the ootheca or egg-case, as was mentioned above. 
When not distended for this purpose, the membrane in question 
