94 
W. F. I’URCELI-. 
eitliei- in the lung-books or in the enclosed air, and observed 
that the entire cnticula of these organs is shed at moulting. 
He doubted their respiratoiy function. 
F. Leydig (’55) found that the “ granulations ” observed by 
previous authors in the lung-leaves of spiders are really 
internal processes, like those in the posterior trachem. 
L. Dufoiir (’56) describes the scorpion’s lung-books (pig- 
ment and reticulation of the leaves, etc.). 
E. Claparede (’63) describes the circulation of the blood, 
with some notes on the lung-leaves, in the spider. 
P. Bertkau (’72) gives a g’ood description of the lung-books 
in spiders, and the earliest account of their growth in young 
spiders. 
C.Chun (’76), from a brief i-emark (p. 42), evidently implies 
that he has found an epithelium with regular cell-boundaries 
on the lung-leaves of Arachnids, but reserves the proof for a 
later occasion. 
H. Lebert (’77, p. 25) makes some very curious observa- 
tions, such as his discovery of a second pair of smaller lung- 
books (Xebenfachertracheen) in other spiders besides Tetra- 
pneumones (e. g. in some Argiopidas); also bifurcate 
saccules. 
J. MacLeod (’80, ’82, ’84) advanced our knowledge greatly 
beyond the works of his predecessors by the use of sections. 
In his first paper (’80) he describes the lung-books as “ un 
faisceau de trachees aplaties, foliiformes” (p. 48), but 
influenced later by the branchial theory he re-casts his method 
of Heating the subject (’82, ’84). His principal paper (’84) 
is, perhaps, the best known of all works on the lung-books. 
B. Bay Lankester (’81, ’85a, ’85b) in his first paper com- 
pares the Inng-books of scorpions with the gill-books of 
liimnlus from actual preparations, and derives lung-books 
from gill-books by a theory. This paper (’81) affected most 
subsequent studies of the subject, and made the development 
and comparative anatomy of the respiratory organs a subject 
of paramount interest in the Arachnida. His later papers 
(’85a, ’85b) describe the circulation of the blood through the 
