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440 On the Nature and Origin of the [May, 
the endotrachea; we hope to show that the so-called “ spiral 
thread” is not spiral in arrangement but simply thickenings of 
the endotracheal membrane, parallel to each other, not necessa- 
rily continuous nor arranged in a spiral manner. For these 
chitinous bands we would suggest the name żænidia (Greek, little 
bands). 
Our observations have been made on the larva of a species of 
Datana, which was placed in alcohol, just before pupation, when 
the larva was in a semi-pupal condition, and the larval skin could 
be readily stripped off. At this time the ectotrachea of the larva 
had undergone histolysis, nothing remaining but the molted en- 
dotrachea, represented by the tænidia, which lay loosely within 
the cavity of the trachea. The ectotrachea or peritoneal mem- 
brane of the pupa was meanwhile in process of formation; the 
nuclear origin of the tenidia was very apparent, and it was their 
appearance which led me to examine the origin and mode of 
development of the so-called “ spiral thread,” and to endeavor to 
trace its relations to the intima (endotrachea) and peritoneal mem- 
brane (ectotrachea). z 
Fig. 1 is a longitudinal section through a secondary tracheal 
branch, showing 
the origin of the 
circular chitinous 
bands, or tænidia. 
At 7 are pieces 0 
six tænidia which 
have been molted; 
ecir are the nuclei 
forming the outer 
cellular layer, the 
ectotrachea or pen- 
toneal membrane» 
Fic. 1.—Longitudinal section of a trachea, showing i send 
the origin of the teenidia or so-called spiral thread. € These nuda 
long slender p!” 
longations around the inside of the peritoneal membrane; these 
. 
;prolongations, as may be seen by the figure, become the tenmi. 
The tænidia, being closely approximate, grow together more . 
less, and a thin endotracheal membrane is thus preci 
= which the tenidia are the thickened band-like portions. 
__ endotracheal membrane is thus derived from the ectotrachea, 0f = 
oo a LENIE 
