TRACHEATA 415 
complete form in the mature female, and appears after the 
ninth or last moult. 
The testis in the male consists of two caeca, placed ven- 
trally in the anterior part of the abdomen ; each passes into a vas 
deferens, and the two vasa deferentia unite together in a small 
vesicle which opens to the exterior just behind the level of the 
pulmonary sacs. In Zegenaria guyoniw the semen is deposited 
on a web constructed for the purpose, and taken up by the 
palpal organs and by them introduced into the spermatheca of 
the female, an operation not unattended by danger, as the 
female, when hungry, has been known to seize and devour 
the small male. The number of eggs laid varies from 
above one thousand (Argiope cophinaria) to two (Oonops 
pulcher) ; they are generally deposited in cocoons. The Lyco- 
sidae carry their cocoons attached to the abdomen of the 
mother, and when the young are hatched they are borne on 
her back till the first moult. Zheridion carries the cocoon 
between the base of the legs, and if it be lost searches about 
diligently till it is found. 
The Araneida are divided into two sub-orders: 
1. TETRAPNEUMONES, with four lung sacs, and as a rule 
four spinnerets. 
2. DIPNEUMONES, with two lung sacs and six spinnerets. 
Sub-order 1. TETRAPNEUMONES. 
These are large hairy spiders which do not weave webs, 
but burrow in the earth, lining their tubular tunnels with a 
thick web. They sit at the entrance of these holes waiting for 
their prey, which, in the case of the gigantic South American 
Mygale avicularia, often takes the form of small birds. Other 
members of this sub-order are Cteniza and Nemesia, the trap- 
door spiders, found in Southern Europe; these genera close 
the entrance of their tubular home with a lid or trap-door. 
Both these genera have two pairs of spinnerets, of which the 
posterior pair are very long and bend up over the abdomen. 
Atypus, the only genus of Tetrapneumones found in Britain, 
has six spinnerets. 
The endosternite, which was well developed in Zimulus and 
