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Psyche 
[September 
commissures between the dorsal and ventral longitudinal 
trunks near to the dorsal trunks (al fig. 2) ; the urinary 
tubules (ur fig. 4) are supplied in the same manner. 
Arising from the stigmatic chamber, beside of the large 
dorsal trunk are several other tracheae. One of these runs 
forward and breaks up into many smaller branches which 
supply the alimentary tract and urinary vessels (to al and 
ur fig. 4). A branch arising from the dorsal trunk near to 
its junction with the stigmatic chamber also sends three 
good sized branches to the urinary tubules (2 fig. 4). 
The Salivary Glands. 
The salivary glands (sg fig. 2) are supplied with tracheae 
arising in a manner similar to those going to the alimentary 
tract. 
The Muscles. 
A study of figure 2 will make clear the supply of tracheae 
to the muscles much better than would a worded descrip- 
tion. 
Discussion 
The present study is necessarily incomplete, because of 
lack of material, and too superficial to allow of any but the 
most general conclusions to be drawn. 
It does seem safe, however, to say that apparently the 
trichopterous, lepidopterous, and dipterous tracheal systems 
are variations of the same general scheme. This statement 
could not be made, however, were it not for the excellent 
works freely cited in the text. 
The Trichoptera, as shown by Palmen (1877), possess 
rudimentary spiracles from which are developed the 
spiracles of the imago. In a study which I have made, but 
which has not been prepared for publication, I found that 
other than lacking functional spiracles, and possessing 
tracheal gills, the trichopterous larval tracheal system is 
very similar to that of the lepidopterous larva. The dipter- 
ous larval tracheal systems vary, as noted by Packard 
(1898), but here we have, in the Cecidomyiidae (Williams, 
1910) open spiracles with a small ventral system, cor- 
responding to the main longitudinal tracheae of the 
