EESriKATOKY OEGANS IN AEANE^. 
89 
Lam-ie and Gough, who examined embryos of Phrynids, are 
not quite clear as to the segmental position of the lung-books. 
Laurie (’94, p. 34) states that the first pair belongs either to 
the first or second abdominal somite, while the second pair 
belongs to the third somite. According to Gough (:02, 
p. G16) the lung-books belong to the first and second ab- 
dominal appendages, but the author does not say to which 
somites they belong. Pereyaslawzewa (:01), on the other 
hand, describes distinct paired appendages on each of the 
first five abdominal somites, the lung-books being formed 
from the third and fourth pairs (p. 194). 
In view of the definite statements made by iSchimkewitsch, 
as well as of the anatomical evidence afforded by the adult 
(see footnote on preceding page), and of the close relationship 
which the Pedipalpi bear to the Aran etc, we may accept as 
certain that the lung-books in the former group belong to 
the second and third abdominal segments, i. e. the eighth and 
ninth post-oral somites, and that the genital segment is the 
second and not the first of the abdomen, as stated by Laurie 
(’94). This would make the lung-books in the Pedipalpi 
directly homologous with the corresponding ones of the 
Araneaj, as represented in the table on p. 86. 
I consider that the pulmonate Arachnids comprise two 
distinct groups, which have separately originated from 
branchiate ancestors, namely, (1) the Scorpiones, and 
(2) the Aranete and the Pedipalpi. To the latter phylum 
some, if not all, of the remaining orders of tracheate 
Arachnida may perhaps be added, but 1 shall not at present 
enter further into the relationships of these other orders. 
Pocock (’93) has already expressed the opinion that the 
Scorpiones, although the most primitive of all terrestrial 
Arachnida, could not have been the ancestors of any other 
orders of Arachnida, because the useful tail would not be 
likely to be lost. Pocock, who based this opinion on grounds 
segment. Recently Taruani (:04, text-figs, on pp. 51, 52, and 121) and 
Burner (:02, :04) have also adopted this view. 
