256 ON THE POISON OF ARANEIDEA. 
belief that spiders are destitute of a labrum, or by 
mistaken notions as to its precise situation. That 
they possess the organ in a low state of development 
is undeniable, as I have distinctly observed it in spe- 
cies belonging to the genera Lycosa, Dolomedes, Sal- 
ticus, Thomisus, Olios, Drassus, Clubiona, Ciniflo, Age- 
lena, Tegenaria, Colotes, Theridion, Linyphia, Epeira, 
Dysdera, and Segestria*. It is attached by its 
base to the superior surface of the palate; but the 
extremity, which is free, and usually round or some- 
what pointed, can be slightly elevated, depressed, 
extended, retracted, and moved laterally at will. To 
apply the term mandibles to organs originating above 
the labrum, and therefore not situated within the 
mouth, must evidently be erroneous ; and I venture 
to anticipate, upon anatomical considerations, that 
future investigations will lead to the conclusion that 
the mandibles of the Araneidea are confluent with the 
palate. 
* Professor Owen has detected a rudimental labrum in spiders 
of the genus Mygale. See his ‘Lectures on Comparative Ana- 
tomy’ (Ist ed.), Lecture xix. Arachnida, p. 257. 
