40 
W. F. PUKCELL. 
yolk also contains blood- corpuscles, vitellopliagous cells, and 
various iiiesoderinal elements, besides fluid. 
Jaworowski’s tracheal trunk and ante-chamber undoubtedly 
correspond in position to the lower part of the septum and 
its funnel-shaped widening, but 1 have found nothing in them 
in my sections which could possibl}’ be taken for trachea}. 
Jaworowski states that the trunk has a nucleated epithelium, 
the nuclei being smaller than those of the pulmonary 
lamellje (p. 62). These may well be, 1 think, the nuclei of 
the mesodermal septa, but I am at a loss to account for the 
tracheal branches and branchlets drawn by Jaworowski in 
his tigs. 1 and 2. At any rate the tracheal nature of the 
structure cannot possibly be maintained so long as no 
embryological evidence at all is advanced to prove that they 
are of ectodermal origin and derived from the same mass of 
cells which form the lung-books. It will be noticed further 
that the lumen of the ante-chamber is closed off from that of 
the tracheal trunk by a diaphragm (p. 68). 
No other investigator has ever found anything like these 
embryonic tracheae, and although Jaworowski (’94, p. 55) 
asserted that Schimkewitsch (’86a, ’86b) had previously 
observed a similar structure, the latter author has recently 
(:06, p. 45) disclaimed any connection between that figured 
by him and those found l)y Jaworowski. 
Scorpiones. — Metschnikoff ('71), Laurie ('90 and ’92j, 
Brauer (’95) and Pereyaslawzew'a (:07) all agree that the lung- 
books of scorpions arise as folds in the wall of the pulmonary 
sac, which according to the first three authors is formed by 
invagination on the posterior sides of the four posterior pairs 
of abdominal a})pendages. According to Pereyaslawzewa, 
however, this sac arises on the anterior side of the appen- 
dages, but it appears to me probable that this author has mis- 
taken the intersegmental folds which separate the sternites 
for appendages, the true appendages described by previous 
authors having evidently already disappeared. 
Brauer states that, so far as he could make out, the oldest 
pulmonary fold occurs at the innermost part of the sac, the 
