THE I’HYLOGEXY OF THE TRACHE.E IX AFvAXE.E. 549 
may possibly represent a strand which became separated 
from 30 when the lateral entochondrite (p. 530, text-fig. 7, t.) 
disappeared. 
From a comparison with the Dysderidm it is evident 
that the trachece of the second respiratory segment in 
Caponia correspond to those of the Dysderidte, and, like 
the latter, are to be considered as entirely homo- 
logous with lung-books, for there is no evidence that 
entapophyses took any part in their formation. 
Tlie receptacula seminis are paired, and consist of an 
enormous dilation of each oviduct apparently at the point 
where the ectodermal and mesodermal elements of the duct 
meet, Tliey are placed nearer the upper part of the abdomen 
just above the area enclosed between the four spiracles, but 
extend for some distance to the front and behind this area as 
well. The ventral wall of each dilation has a cuticular 
lining, but the dorsal wall and the greater part of the side 
walls have none. Apparently the latter represent the meso- 
dermal part of the oviduct and the former the ectodermal 
part. The ventral wall with its cuticula is continuous with 
the basal portions of the oviducts, which open into the lateral 
ends of the unpaired median portion of the duct. This 
latter again opens into the epigastric fold along a wide cleft 
occupying about one half of the distance between the two 
anterior trachem. The spacious lumen of each receptaculum 
contains coagulated stainable matter and mimerous sperma- 
tophors. Tills form of receptacula is apparently quite unique 
amongst spiders, the usual ones which open directly into the 
epigastric fold, and are evidently invaginations of the body 
integument, being quite absent in Caponia. 
Ckxeral Cox'clusioxs. 
A tracheal system may be imagined to have been evolved 
out of a lung-book in either of the following ways : 
(1) The pulmonary saccules may have been converted into 
