204 
Psyche 
[Aug.-Oct. 
terlabium, and on each side of it are the palpigers pgr, which 
bear the labial palpi Ip. The palpigers are larger and better 
developed on the other side of the labium (see Fig. 10, pgr). 
The labiostipes Is bear the glossa gl and paraglossa pgl. When the 
glossse and para-glossse unite to form a single median structure, 
they are termed the ligula. The labial palpi have a membranous 
region at the tip of the terminal segment which is supplied with 
sense organs. 
It has long been known that the labium is made up of the union 
of two appendages like the maxillae, which are distinct in the 
embryo; but it is not known what parts of the maxilla corres- 
pond to the parts of the labium in every case.. The earlier in- 
vestigators thought that the cardines (pleural of cardo) unite to 
form the mentum, while the palpifers form the palpigers, the 
stipites, (pleural of stipes) form the labio-stipites, the laciniae 
form the glossae, the galeae form the paraglossae, and the maxill- 
ary palpi form the labial palpi, when the maxilla-like append- 
ages unite to form the labium. The only matter which seems to 
be in doubt is whether the united cardines form the mentum mm, 
or whether they form the small median region il of Fig. 11. I am 
inclined to think that the small region il, rather than the mentum 
mn, represents the united cardines, since Holmgren states the 
mentum is formed in the embryo behind the labial segment, so 
that the basal segments of the maxilla-like appendages of the 
labium, which unite to form the underlip can have nothing to 
do with the mentum, if the latter is formed behind the labial 
segment. The whole matter is still very puzzling, and should be 
re-investigated with a view to determining exactly what struc- 
tures represent the united cardines of the appendages which 
form the underlip. 
Of the other external features of the head which are of any 
great interest, there remain to be considered only the antennae. 
In the roach these are long, slender, delicate, filiform or flagel- 
late structures composed of a great number of segments. At 
the base of each antenna is a narrow ring-like sclerite ban of 
Figs. 5 and 7, surrounding the antennal membrane at the base 
of the antenna. This ring-like antennal sclerite is called the bas- 
antenna, or antennale. (Yuasa, 1920, uses the form “anten- 
