310 
Hermaphroditism etc. in Pediculus 
the $ plate which thereby acquires symmetrical lateral extensions; (7) the 
extensions vary in size down to their complete disappearance, leaving the 
$ plate alone. The form of the several plates may be regular, asymmetrical, 
or the margins may be frayed 1 . 
Genital organs. 
(A) The external genitalia. 
The large number of hermaphrodites (155) examined by us has yielded 
a complete series of gradations in which the external genitalia of both sexes 
coexist and occur in varying proportions. This gradation is rendered clear 
by the following grouping: 
Group 
1 
2 
Armature 
Complete 
99 
6 Complete but deformed 
7 Reduced and deformed 
O 
° 99 99 99 
9 Reduced to an invaginated sack or 
completely internal, or reduced to 
an internal sack 
10 Absent* 
$ Armature 
Absent* 
Represented by gonopodial spots or in¬ 
ternal sacks, lobes absent f 
Rudimentary gonopods, uni- or bi¬ 
lateral, lobes absent 
Complete but reduced, lobes absent 
Complete, lobes absent 
99 99 99 
„ ,, rudimentary 
„ ,, present 
Complete in all respects 
Complete in all respects 
* But the hermaphrodite character was indicated by the presence of dorsal bands and the 
structure of legs I and III, or by internal genital organs. 
f By “lobes,” for brevity sake, are meant the posterior abdominal lobes that characterize 
the $. 
The fairly frequent coexistence of the two sexual armatures in an almost 
complete form is probably explained by the circumstance that the points 
of origin (Anlagen) of the two sets of organs are slightly separated; con¬ 
sequently the armatures, during their development, do not intrude on each 
other. 
The invaginations, occurring commonly in hermaphrodites of Pediculus , 
represent parts of the external genitalia, either £ or $. To understand the 
origin of the invaginations, it should be remembered that the genital armature 
is rapidly formed during the last larval stage, its development commencing 
with an intense proliferation inward of the hypoderm. Immediately before 
the last moult, the newly formed genitalia appear more or less folded beneath 
the larval cuticle, but, when the insect moults, these organs acquire their 
definite form. If we assume that the proliferation of the hypoderm, for 
1 Curiously enough the male ventral plate in Pediculus appears to have escaped notice hitherto 
although it is a striking feature. This is doubtless due to previous observers not having studied 
well pigmented specimens where the plate is most in evidence. The plate serves for the origin 
of the retractor muscles of the male copulatory apparatus. 
