RESPIRATORY ORUANS IN ARANE^. 
59 
1. sp. m. 10), which pass posteriorly and attach themselves to 
the medial and lateral parts respectively of the base of the 
left anterior spinner. The same muscles are seen in fig. 28. 
The smaller posterior portion of the tendon is further con- 
nected with the lateral edge of the tracheal pedicel by a 
small transverve column of cells [tr. vi.), apparently of a mus- 
cular nature and plainly corresponding to the little tracheal 
muscle found by Schiinkewitsch (’84, p. 66, PI. ii, fig. 6)^ 
and subsequently also by Lamy (:02, p. 160, PI. viii, figs. 4, 
5) in the adult of Epeira. Schiinkewitsch considers these 
muscles to serve the purpose of closing the lumen of the 
tracheal pedicel, which in the adult, as well as in the young, 
is strongly compressed dorso-ventrally. The lateral part of 
the tracheal proliferation lies under the two spinner muscles 
and the entochondrite, t., and the posterior edge of the 
proliferation is apparently wedged in between the spinner 
muscles and the transverse tracheal muscle. 
'I'he lumen of the whole trachea at this stage is lined with 
a smooth but strong cuticular membrane {cn., fig. 29a). The 
great ventral longitudinal muscles {v. 1. m. 10) of the tenth 
somite are stretched some distance above the trachea between 
the entochondrites t. 9 and t. 10. 'I’he former of these 
entochondrites is attached as before to the anterior end of 
the tendinal portion of the trachea (er. t. 9), while the latter 
lies above the spiracle and is attached to a long hollow 
entapophysis from the posterior side of the anterior pair of 
spinners. 
After the second post-embryonic moult (stage 9) the trachete 
appear for the first time as a fully functional respiratory 
organ. In shape they are not much changed, except that 
the lateral proliferations now branch at the ends into two 
smaller trachejB, but beyond these I could not find any other 
brauchlets at this stage. 'The chitinous lining is now covered 
(except in the pedicel) with the palisades of hooped (anasto- 
mosing) spines, ahso found in the adult spider, which keep 
' In the figure the muscle is marked ep., hut in the text (p. 88) these 
letters stand for the chitinous tliickening. 
