36 
W. F. PUJiCELL. 
time of hatcliiug there are about seven or eight developed 
saccules. At the time of the second moult there are perhaps 
twelve to fourteen, while in the adult about thirty-four or 
thirty-five appear to be present, but I cannot state the exact 
numbers with certainty. 
Critical remarks on the literature. — Aranefe. — According to 
Locy (’86,p.81) the in-foldings for the lung-books in Agelena 
ngevia arise late in the period of the reversion. From his 
figure (fig. 73) and description of “early stages” (p. 89), in 
which the lung-books appear as extensive gi’oups of cells 
with the nuclei arranged iu parallel rows, as well as from the 
fact that he makes no mention of any connection with the 
abdominal appendages, it is clear that Locy was really deal- 
ing with late stages after the appendage had already sunk 
into the body and long after the earlier saccules had been 
formed. Of the formation of these latter he gives no 
account. His account of the formation of the definite septa 
has already been dealt with on a previous page (p. 31). 
Bruce^s (^86a, ’86b, ’87) statements may be dismissed as di.s- 
proved by later researches. Both Kishinouye (’90) and 
Simmons (’94) are of opinion that Bruce (’87) has misinter- 
preted the parts in his figures Ixxix and Ixxix'. Certainly 
the fold L' is not a pulmonary fold, and is not on the anterior 
surface of the first abdominal appendage, as Bruce supposes 
it to be. 
Simmons (’94) states that the pulmonary sac arises as an 
in-pushing behind and under the abdominal appendage, “ so 
that eventually a pit is formed, actually extending into the 
general body surface.” The pit is considered as bounded on 
its outer side by the appendage itself, its outer wall being- 
described as “the morphologically posterior surface of the 
appendage” (p. 217), which is represented as lying flat on 
the body surface and directed backwards. The opening of 
the pit under the posterior or distal end of the appendage 
persists as the spiracle. The outer wall of the pit “has its 
ectoderm thrown into folds, the rudiments of the leaves of 
the lung-book,” and sections of early stages are figured, one 
