8 . THE BRITISH WOODLICE. 
(b) Masses of cellules in the head, very greatly developed in 
Ligia oceanica (but numbering scarcely more than ten inZOntscus 
vfs, 
¢., "Comemussures 
=< ao SUNT ORANG 
Sit = wed uniltiig 
eS | ORs bo fori 
Tin | fae 
DS eble cord 
Letory 
FIG. 19.—THE NERVOUS SYSTEM. 
(Oniscus asellus.) 
or less continuous in 
Oniscus (5, p. 265). 
(7) The digestive 
glands have also been 
shown to be excretory 
(5, Pp. 270). 
Nervous system.— 
The nervous system con- 
sists of paived ganglia in 
the head, above the 
alimentary canal which 
send off nerves (commis- 
suves) that meet below, to 
form a double nerve cord 
with ganglia at intervals 
(see fig. 19). 
Reproductive organs. 
—In the female there are 
asellus), which have no external 
opening. They also function as 
excretory organs (5, p. 263), and 
have been called “ cephalic nephro- 
cytes.” 
(c) Other “branchial nephro- 
cytes”’ are situated on the dorsal 
surface between the last thoracic and 
the first abdominal segments, as well 
as between those that follow, with 
the exception of the last two; they 
are in distinct patches, one on each 
of the middle line in Ligia, but more 
Vhoractc segneent 
} OVARIES, 
i 
Se ‘ 
BON 
y 
‘ 
\ 
FIG, 20,—FEMALE REPRODUCTORY ORGANS, 
(Ontscus asellus.) 
a pair of ovaries in the positions shewn in fig. 20; and ducts run 
to the underside of the fifth thoracic segment. 
