THE PHYLOCiENY OF THE TPACHE.E IN APANIOE 
555 
the medial trunks of Filistata^ -wliicli this author has shown 
to be entapophyses. 
In both groups more complicated types than the two simple 
ones just described are frequently found, and it is important 
to notice that this complication takes place along different 
lines in each group. Thus in group A some Sicariidae and 
Palpimanidae were found by Lamy (p. 176, fig. 15, and 
p. 188, fig. 30) to possess branched tracheae, the branching 
being confined to the lateral or tracheal trunks. In group 
B, on the other hand, in all cases where the lateral and 
medial trunks can be identified from Latny’s figures and 
show different degrees of development, it is invariably the 
medial trunks which show the greatest complexity and the 
highest degree of development as respiratory organs.^ This 
rule appears to me to furnish the key to the phytogeny of 
the tracheae in these spiders. We may also fairly deduce 
fi’oni it that the medial tracheae must be more efficient as 
respiratory organs than the lateral tracheae are, and the 
reason for this, as I have already pointed out (:09), may 
be their position in the large ventral sinus containing venous 
' This is self-evident from Lamy's excellent figures in many cases 
e. g. CEcobiidie (Lamy, p. 170, fig. 10). Argiojjida; (p)). 107 — 100, figs. 
38 — 1'2), TliomisidiK (pp. 20f)anJ207, figs. 40 and oO), and Agelenida; 
(pp. 214 — 216, figs. 59 — 61). In arborescent types of tracheae (see my 
paper, :09) it is not so self-evident, but the same conclusion may 
Ije deduced from the great similarity which this form of trachea shows 
to that of the Attidai, of which the identity of the parts is known from 
the embryology. There remain, however, certain Dictynidae and 
Agelenidse, the homology of whose trachea} cannot be ascertained with 
any degree of certainty from Lamy’s figures. In Argyroneta 1 found 
(:09), from the position of the imiscles and entochondrites, that the 
entire trachea appears to have been derived from the medial trunks, but 
1 have had no oj^portunity of examining any of the other forms, viz. 
Dictyna (Lamy, p. 169, fig. 8), Antistea (p. 213, fig. 57), Cybaeus 
(p. 217, fig. 62), and Chorizomma (p. 219, fig. 64). If these, too. coidd be 
l)i'Oved to follow the rule given above, the arguments in the following- 
pages would be greatly strengthened. I may add here that in the 
marine Agelenid, Desis tubicola, Poc., the trachea}, which have not 
been hitherto described, closely resemble those of Attus. 
