64 
W. K. PUKCEU,. 
Attus floricola (Hg. 28) at tlie same stage (stage 6). 
They are, however, mucli further apart, and, therefore, with a 
wider intertracheal infolding connecting them, the latei’al 
proliferations being also more pronounced. Further, each 
plate is much tliinner in the middle and lateral region than 
at tlie base and along the anterior and medial mai’gins. 
In embryos one to two days after hatching (stage 7) the 
tendinal portion of each plate has considerably increased in 
length and is, like the rest of the plate, very thin, except at 
the apex, where it rather suddenly swells out and ends in a, 
thick knob to which the eutochondrite is attached. 
After the first post-embryonic moult (stage 8) the tendinal 
portion of the trachea has much the same appearance as in 
the previous stage, except that it has increased in length, 
but the lateral proliferations have grown for some distance 
in a lateral direction close to the hypodermal covering of the 
body and are now provided with a distinct lumen in the form 
of a very fine canal lined with chitin and communicating 
with the spiracle. The chitinous lining both of this and of 
the tendinal portion is smooth at this stage. 
At the second moult (stage 9) the trachea assumes its 
permanent shape. The chitinous lining, except in the pedicel, 
becomes provided with the usual anastomosing spines and 
the lateral proliferations increase considerably in length, 
still growing in a lateral direction. The pedicel and the 
canal of communication also appear. In fig. 30 (just before 
the second moult) the hooped spines (ft'pt.) of stage 9 have 
already appeared in I’eadiness for the moult. 
Both in this stage and in the previous one the lumen of 
the lateral proliferation {tr. prol., fig. 30), in its basal region 
at least (i. e. near the pedicel), is eccentric, lying posteriorly 
to the axis, the posterior wall of the trachea being much 
thinner than the anterior wall, which contains nearly all the 
nuclei. Towards the apex this wall becomes much thinner 
and the lumen lies practically in the middle. This eccen- 
tricity of the lumen is significant of the origin of the lateral 
trachea, and may be at once understood if we remember that 
