42 
W. F. PUKCELF;. 
lung-books in spidei-s, the descriptions of MacLeod (’84) aud 
Berteaux (’89) being unsatisfactory in this respect. Berteaux’s 
account of the chitinous structures (spines, etc.) of the lung- 
books is, however, very detailed and the best we possess, but 
his description of the bi-nucleated cell-columns in tlie septa 
as nnicellnlar structures is misleading and not in accordance 
with the embryological facts, since these columns are formed 
by the fusion of opposed cells in two separate epithelia. 
Both MacLeod and Berteaux made a curious error regard- 
ing the free edges of the septa. The edges of the septa they 
describe as being free, not only along the posterior border 
but along tlie posterior part of the lateral side as well. As 
a matter of fact tlie lateral sides of the septa are never free, 
but may have the appearance of being so in horizontal 
sections through the dorsal procurved portion of the ante- 
chamber. The apparently free edge is merely that of a 
septum with its lateral part cut off by the razor, hence the 
irregularities in its occurrence observed by these authors. 
'I’hat these lateral edges are not free can easily be demon- 
strated by examining the lung-books under a hand-lens after 
treatment with caustic jiotash, and I can strongly recommend 
this old-fashioned method to anyone who wishes to obtain a 
clear idea of the coarser structure of the lung-books in a short 
time (see fig’. 20). It will be found much more satisfactory 
than if one were to rely on sections only. 
Bbrner (:04) has recently stated that the se})ta are placed 
more or less vertically in the majorit}^ of the Aranete, and 
has thrown doubt on MacLeod’s well-known diagrams, in 
which the septa are i-epresented as lying horizontally. 
I have examined one or two species of most of the larger 
families and I found the septa as nearly horizontal as they 
could well be in the following Lipneumonous spiders : 
Attidm (Attus floricola), Lycosidm (Lycosa Uar- 
lingi), Agelenidte ('I’egenaria domestica, Textrix 
lycosina), Clubionida) (Clubiona holosericea, Paly- 
stes sp.), Thomisida) (Philodromus f uscomargina- 
tus), Theridiid^ (Theridion lineatum), Drassidte 
