6 THE BRITISH WOODLICE. 
from moist air, while the outer division (or exopodite) acts as a 
protecting cover (fig. 14). In Porcellio, air-tubes (tracheae) may 
be present (see below). 
ABDOMINAL 
APPENDAGES In the male, the first 
‘ee two pairs of abdominal 
Byes Bearing appendages are specially 
a modified, the inner divi- 
6 Unepodl sions (endopodites) being 
L long and pointed (figs. 15 
i vomnw Lplopodite and 16). The last pair, 
rie £ x0podile or tail appendages, in the 
FIG. 13.—THE UNDERSIDE OF THE ABDOMEN OF A male are often consider- 
FEMALE. (Oniscus asellus.) ably larger than in the 
female, and the form of these structures is sometimes of 
value in classification, 
Alimentary canal.—The 
main portion of the alimentary 
system is, practically speaking 
a straight tube (fig. 17). Its 
first part (not shown in the 
figure) is a narrow gullet, which 
after passing through the nerve 
collar dilates to form a sort of FIG, I4.—A TYPICAL ABDOMINAL 
x : APPENDAGE. 
stomach. Into this the secretion (Oniscus asellus.) 
of four digestive glands is poured by two ducts. These glands 
have a somewhat striking appearance, being yellow tubes spirally 
FIG, I5.—THE FIRST ABDOMINAL FIG. 16.—THE SECOND ABDOMINAL 
APPENDAGE OF THE MALE, APPENDAGE OF THE MALE 
(Oniscus asellus.) (Ontscus asellus.) 
coiled, and they end blindly. From the stomach the intestine 
runs to the hinder end of the body and passes under the heart. 
