RESPIRATORY ORGANS IN ARANE.E. 
13 
in a spider (Agelena ntevia), and lie is the first to give an 
account of the transformation of the embryonic epithelial 
foldings into the definite pulmonary septa (lamellee) with their 
chitinons coverings. According to him the lung-books arise 
as a pair of invaginations late in the period of the reversion, 
but he makes no mention of their connection witli appeu- 
d a.<res. 
Bruce (’86a, ’86b, ’87) is of opinion that the pulmonary 
folds in spiders are formed on the anterior surface of the first 
abdominal appendage, which subsequently becomes involuted, 
so that its anterior surface with the folds now faces the pos- 
terior end. Probably two abdominal appendages are invagi- 
na ted for each lung-book. 
Schimkewitsch f’87; also in ’86a and’86b, teste Jaworowski, 
’94) states that the lung-book arises as an invagination of the 
ectoderm and forms a true trachea, consisting of a main trunk 
divided into five branches, in the embryo of Lycosa saccata 
just before hatching. Recently, hovvevei', Schimkewitsch 
(:06, pp. 45, 46, footnote) has withdrawn this interpretation. 
Kowalevsky and Schulgin (’86) merely note that the pul- 
monary sacs in the scorpion (.\ndroctonus ornatus) arise 
as simple invaginations into a space containing plenty of 
blood. 
IMorin (’87) found that 'the lung-books in the spider 
(Theridion) arise from a pair of ectodermal invaginations 
at the base of the first pair of abdominal appendages, which 
themselves become the lung-opercula. In his later paper 
(’88) he appears to have given more details of the formation 
of the lainelhe, of Avhich those nearest the operculum are 
furthest developed (teste Jaworowski ’94, pp. 57 and 58). 
Laurie (’90) states that in the scorpion (hluscorpius 
italicns) the four last pairs of abdominal appendages are 
pushed in on their posterior part, so as to form shallow, cup- 
like cavities, which later on are divided up by lamellm growing 
down from their upper ends (pp. 125 and 127). A later stage 
with lamellae is also described (p. 129). In a later paper 
(’92) he deals with the development in Scorpio fulvipes. 
