THE PHYLOGENY OF THE TEACHEiE IN AEANEH:. 521 
same family, as in the Agelenidae, or between allied families, 
such as the Dysde ridge and Oonopidge — nor that other 
tracheal characters, such as the acquisition of the respiratory 
function by the ectodermal tendons of the tracheal segment, 
which I have shown to have taken place in most spiders, may 
not have a much higher phylogenetic value. 
Before entering upon this subject I wish to consider a 
certain remai’kable conclusion drawn by Lamy, viz. that in 
spiders neither the lung-books nor the trachete are the more 
primitive organs (p. 264), both having been produced simul- 
taneously and replacing one another (p. 265). The sole 
difference Lamy sees between these two organs lies in their 
special mode of branching, lamellate branches pi'oducing 
lung-books and tubular ones trachejB (p. 267). The branchial 
origin of the lung-books is discarded by him as unnecessary 
and the formation of the tracheal organs is considered to be 
the consequence of the respiratory function taking place in 
the same conditions in all air-breathing Arthropods (pp. 266 
and 267). 
Lamy arrives at the above conclusion by the following 
ai’guments (p. 264): — (1) The Dysderidm and the Capo- 
niidm come very near together, approaching one another in 
several characters, and ought, therefore, to be regarded as 
equally primitive. Nevertheless, in the latter, the first pair 
of lung-books is replaced by a pair of tracheae, which strongly 
resemble those which replace the second pair of lung-books 
in the Dysderidm. The fact that one sees the trachete 
indifferently replacing the lung-books in these two somewhat 
primitive families indicates that neither organ is to be re- 
garded as more primitive than the other. (2) The same con- 
clusion results fi’om the fact that we find amongst the 
Araneae verae' another family, the Hypochilidae, which, 
* Simon divides the spiders as follows: Aranese tlieraphosai (= 
Mygalomorphai, Pocock -t- Liphistius), including all 4-limged 
foi’ms except the H ypochilida?. Araneai verse (Arachnoniorphse. 
Pocock), including the Hypochilidai and all dipneumonous and 
apneuinonous spiders. 
