74 
W. F. rURCELL. 
between the entoclioudrite and the vestibule is homologous 
with the much longer but corresponding portion of the 
medial tracheal trunks in Araneus, Tegenaria, etc. 
Thus, the medial trunks in Filistata, Palpimanus 
and Scytodes are homologous with the entire medial 
trunks in Araneus, etc., and not merely with their 
unspined, fibrous, apical portion, as Lamy suggests. 
The unspined portion of the medial trunks in Filistata, 
Palpimanus and Scytodes may well be compared to tlie 
trachem of a young spider previous to the second moult 
(staged), while this organ is still in its primitive spineless 
condition. (Compare the transverse section, fig. 29a, of 
the medial tracheal trunk of a young Attus with that of the 
cuticular lining of the entapophysis of Scytodes given in 
fig. 39.) 
In the pulmonary segment the unpaired median entapo- 
phvsis of a Scytodes has its exact parallel in the unpaired 
median entapophysis of such forms as Lycosa Darliugi, 
described on p. 51. We thus see all the variations of the 
pulmonary entapophyses repeated in the tracheal segment. 
IX. The Entapophyses of the Third and Fourth Abdo- 
minal Appendages (The Spinners). 
These tendons are unconnected with the respiratory org-ans 
and need only be briefly described. They arise at a very 
early stage, being formed out of the post-appendicular grooves 
{(jr., fig. 4), which appear behind the third and fourth 
pair of abdominal appendages shortly before the beginning 
of the reversion (stage 1). At the time of the appearance of 
the first pulmonary furrows (stage 2) these grooves have 
deepened and become more pronounced (figs. 5 and 5a), and 
they may be easily followed through all the later stages (fig. 
6).^ At the end of the reversion they form invaginations {ec. 
' I may point out that no trace of a lateral proliferation corresponding 
to that of the pulmonary and tracheal sacs is ever found in connection 
with these grooves. 
