BESPIKATORY OEGANS IN AEANBiB. 
39 
ot: the septa run parallel to the longitudinal axis of the 
abdomen instead of at right angles to it, as they do in Attus 
floricola, etc. Now if we compare my figs. 13b and 17 
of transverse sections with Jaworowski’s figs. 3 and 5/ which 
come just in between mine in point of development, it will be 
seen that the lung-books of botli species exactly correspond, 
so that the free edges of the septa cannot run longitudinally 
to the body axis. In fact, Jaworowski has evidently mistaken 
the direction of the folds, which are seen laterally in his 
figs. 3 and 5 and not from their free edges ; and, moreover, 
the funnel-shaped area which he calls the ante-chamber in 
his sagittal sections is not the ante-chamber at all. 
The trunk of the embryonic trachea, according' to Jawo- 
rowski, extends dorsad from the apex of the ante-chamber 
and then divides, the branches reaching to the dorsal blood- 
vessel and subdividing into smaller brancblets. These have 
sometimes the appearance of a cuticular tube provided with 
regular internal thickenings (fig. 6). Ultimately both trunk 
and branches degenerate and disappear, only the “ ante- 
chamber'’ remaining to form the lung-book. 
In the later stages of the spider-embryos which I ex- 
amined, I find the yolk-mass continuous along the median 
region but divided towards the sides by partial septa, which 
are transverse and doubtless of mesodermal origin. The 
surfaces of the yolk are lined with very thin Hat cells, and the 
intra-septal space between these two layers of cells contains 
muscles, blood-corpuscles, and a number of large vitello- 
phagous cells resembling those marked i'it. in my figs. 16d, 16e, 
17, etc. Ventrally the intra-septal spaces widen out, the 
widened part appearing funnel-like in stigittal sections (see 
tig. 41, which shows three such septa). The lung-books lie in 
the ventral widening of the septum between the eighth and 
ninth segments. The space between the lung-books and the 
‘ The author calls these " frontal sections,” hut since the abdomen is 
inclined ventrally to the longitudinal axis of the cephalothorax, frontal 
sections of the hitter would cut the abdomen more transversely than 
frontally. (See Locy’s fig. 10 or Korschelt and Heider, p. 585, fig. 372b. J 
