360 Anatomy and Physiology of the Family Nepida. [i 
the sixth abdominal segment comparatively small, and the c 
setæ undeveloped. gis} 
Adult—The ventral surface is smooth, the dorsal surface pi 
cent, the stigmata totally obliterated, and the caudal sete 
oped. -A 
The tracheary branches are distributed to all the organs 
body, so that the chemical processes of respiration are 
throughout the body instead of at special points. From i 
stigmata,two main trunks extend along the abdomen on € 
of the heart, giving off and receiving branches which af 
among themselves. The large trunks are connected by 
of tubes running below the intestines. In the larva, 
from the spiracles join the main trunks, and in the adult, at 
obliteration of the spiracles, these branches are still foun 
attached to the integument. The distribution of trache® 
muscles and organs of the forward part of the body, 1s \ 
tiful; large branches extend into the legs and wings. 
mesothorax the nervous ganglion rests on a triangle of 
Here, too, connected with the trachea, are several air sacs, © 
are inflated before flight. The dorsal and ventral walls 
abdomen are connected by two vertical rows of muscles, 
are doubtless concerned in respiration. | 
Three kinds of trachea: are found in these insects: tM 
icular and parenchymatous. All the main trunks ane 
of the respiratory system are composed of tubular 
as shown by Minot, consists of an external nucleated 
with two internal layers, in one of which is bee 
thread that keeps the tube open. This spiral filamen! 
tinuous, but separate in each branch, and conte 
parallel pieces, each of which tapers to a point at 
and thus is lost. The vesicular trachea of the air 
differs from the tubular trachea, in lacking pe 
have made no study of the parenchymatous 
Dufour as occurring in Nepa. It consists, @ 
author, of several pouches covered by a fine, 
within which, minute tracheary branches a° Si 
pouches are situated in the thorax under the >m 
B. Tue Function oF REPRODYY 
The function of reproduction, which includes 
development, is here confined to generation: « 
