THE THYLOGENY OP THE TRACHE.E IX AEAXE.E. 543 
minute, sharp, conical spines, and. with some longer ones 
towards the apex. 
The hypodermis of the upper and posterior sides of the 
anterior compartment, and especially that of the anterior 
side of the posterior compartment, is much thicker than 
elsewhei’e, and its cuticula has a corrugated appearance 
in sagittal sections, and stains more deeply than the adjacent 
cuticula does (fig. 8). Plainly the whole of this structure 
has some function other than respiratory. The hypodermis 
bearing the three rods is connected at base by means of a 
strand with some cells or fibrous tissue, which may be a 
nerve (fig. 8, nv.). As, however, the specimens were not 
especially preserved for histologdcal purposes, it is impossible 
to say anything definite about the character of these struc- 
tures, except that the rods certainly strongly resemble sense 
organs. 
There are well-developed, transverse, intertracheal folds of 
the integument connecting the spiracles of each pair and 
already indicated by Bertkau in his figures. That of the 
posterior pair (fig. 0, ir.fd.) encloses a spinous canal of com- 
munication (p. 545, text-fig. IG, can.), which connects the 
lumens of the short main trunks {c.tr.) with one another. In 
the anterior segment there is no spinous canal of communica- 
tion, although the lateral parts of the fold are directly con- 
tinuous with the pedicels of the anterior pair of tracliete. 
'J'he well-developed anterior (epigastric) fold (text-figs. 16 
and 18, ep.fd.) is strongly inclined forwards or even hori- 
zontal, especially throughout the median half, where the 
genital duct opens into its anterior wall. Each lateral fourth 
of the fold, lying (in the female) between the opening of the 
genital duct and the tracheal pedicels, appears twice bent 
(text-fig. 18), first upwards or slightly backwards, and then 
more sharply forwards and downwards, the whole of the 
anterior deflected portion (1.) serving for the attachment of a 
broad and powerful muscle (Xo. 4 in text-figs. 16 and 18). 
Near to the trachea the upper part of the fold is somewhat 
inflated, and produced upwards to form a conspicuous enta- 
