108 
W. V. PURCELL. 
Figs. 23a and 23b. — Similar sections of the same in the regions 
indicated in fig. 20. Fig. 22a shows the cuticnla only. 
Fig. 24. — (Zeiss oil im., IV.) Linyphia triangnlaris (ad. (J). 
Sagittal section through the vestibule of the trachea in the region indi- 
cated in fig. 25, showing the cuticnla only. 
Fig. 25. — (Zeiss C, IV, caixstic potash.) Linyphia triangiilaris 
(ad. ? ). Cuticnlar skeleton of basal region of tracheal system. 
Fig. 26. — The same as fig. 24, hut in the median plane along the line 
indicated in fig. 25. 
PLATE 6. 
Adult or snh-adult spiders. 
Fig. 27. — (Zeiss F, I, hot ale. suhl.) Embryo of Attns floricola at 
the stage with 5-6 pulmonary furrows. Reconstruction (made from 
tlie same series of sections as figs. 6 and 6a) of the right pulmonary and 
tracheal appendages seen from their inner side. The only mesodermal 
elements shown are the two segmental tubes, sej/. f. 8 and 9. The 
l)asal outlines of appendages 1-3 are indicated by dotted lines, as are 
also the lumens of the pulmonary and tracheal sacs. 
Fig. 28. — (Zeiss F, I, hot aqueous subl.) Embryo of Attus 
floricola after the reversion. Reconstruction from transverse sec- 
tions of the rudimentary trachea), together with the muscles and ento- 
chondrites attached to the right half. The sketch is imagined as taken 
directly from above, the anterior part being therefore higher in the 
figure than the posterior part (cf. also figs. 41 and 43 of the same 
stage). The rudimentary lumen is outlined by the dotted line. 
Fig. 29. — (Zeiss F, I, hot ale. subl.) Young Attus floricola, 
after the first post-embryonic moult. Reconstruction of the tracheal 
system (imagined as taken directly from above) together with the 
muscles and entochondrites connected with the right half and some of 
those on the left. 29a (Zeiss oil im., IV). Transverse section 
through a right medial trunk at the line indicated in fig. 29. 
Fig. 30. — (Zeiss y^ oil im., II, hot ale. snbl.) Young Agelena 
labyrinthica just l>efore the second post-embryonic moidt. Sagittal 
section through a lateral tracheal trunk and the hypodei-mis below it ; 
the cuticnla of the second moult is already formed. 
Fig. 31. — (Zeiss C, III, caustic potash.) Attus floricola (ad. ? ). 
Tracheal system. (The terminal portions of the secondary tubules are 
not drawn in.) 
Fig. 32. — (Zeiss C, III, equal parts of Flemming’s sol. and abs. ale.) 
