428 TRANSFORMATIONS OF INSECTS. 
thorax by a broad base, the hinder legs being joined on to the 
thorax close to it. Four legs are supported by the thorax on 
either side, and the ocelli mark the front of the upper part of the 
head, which is also joined by fusion, and not by a neck to the 
thorax. In front of the rounded margin of the head, before the 
eyes, are the long and stout jaws, one on each side, and they look 
like the ends of a stout pair of scissor blades. A palp projects 
the scorpion. ( Scorpio occitanus.) 
from either side of the base of the jaws, and looks like a leg, but it 
ends in a peculiar structure, and is not a locomotive organ. 
The abdomen is not jointed and has no visible segments ; the 
web spinning apparatus exists ; and this spider does not breathe by 
tracheae but by pulmonary sacs. 
The integument of the spiders is precisely analogous to that 
of the true insects, and has the same chemical constitution. In 
the order of the pulmonary (sac breathing) Arachmda it may be 
