14 
W. F. PURCELL. 
Kishinouye (^90') confirms the statement regarding the lung- 
books and the opercula contained in Morin’s earlier paper 
(’87), and adds that that wall of the invagination which faces 
the distal end of the appendage is much thickened, filling the 
interior of the appendage, the cells becoming after a while 
arranged in parallel rows to form the septa. He examined 
Lycosa, Agelena, Theridion, Epeira, Dolomedes and 
P h o 1 c u s . 
Simmons’ (’94) paper is the most important that has yet 
appeared on the development of the spider’s lung-books, and 
was based on embryos of Agelena nmvia and Theridion 
tepidariorum. He confirms Morin’s and Kishinouye’s state- 
ments regarding the formation of the pulmonary invagina- 
tion, and was the first to describe and figure an early stage 
of the formation of the pulmonary septa (lamellae), which he 
states arise as infoldings upon the posterior surface of the 
abdominal appendage in the same manner as described by 
Kingsley for the gills of Limulus. 
Javvorowski (’93 and ’94) describes the presence in a spider 
embryo (Trochosa) of embryonic tracheae, which ultimately 
becomes rudimentary, excepting the portion adjoining the 
spiracle. The wall of this portion is thi-own into folds and 
persists as the lung-books. The author thus totally differs 
iu some most important points from all his predecessors. 
’I’liese tracheie arise from invaginations under the abdominal 
appendages, the latter becoming the opercula (’95, p. 43). 
Jaworowski also gives a valuable account of the formation of 
the definite pulmonai’y septa out of the folded embryonic 
epithelia. 
According to Laurie (’94) the embryonic abdominal 
appendages are not paired in the Pedipalpi, but stretch 
right across the abdomen, and in Phrynus the lung-books 
evidently arise as foldings of the posterior wall of an appen- 
dage. 
Brauer (’95) confirms Metschnikoff’s and Laurie’s observa- 
tions on the earlier stages of the pulmonary invaginations at 
the base of the four posterior pairs of abdominal appendages 
