EESPLKATOKY ORGANS IN AEANEiE. 
15 
in scorpions, and giv^es the best account of the early stages 
of the pulmonary folds (in Euscorpins car pat hie us). 
In my own paper (’95) the appearance of the earliest pul- 
monary folds on the free posterior side of the first pair of 
abdominal appendages in Aranem is described. 
Sophie Pereyaslawzewa (:01) investigated the earliest 
appeai-ance of the lung-books in Phrynidmin Phryniscus 
b a c i 1 1 i f e r and the later stages in Damon m e d i u s. Accord- 
ing to her the lung-books are formed from the third and 
fourth abdominal appendages, which belong to the third and 
fourth abdominal segments (p. 194). The outer integument, 
the cuticula of which is regularly wrinkled (fig. 61), is deeply 
infolded into the body behind the third and fourth appen- 
dages to form the lung-sacs, the grooves in the invaginated 
wrinkled surface deepening to form the saccules, while the 
ridges become the septa (pp. 248-252). The embryonic 
septa are also described (p. 262) and figured (fig. 69). 
Gough (:02) states that the lung-books in an embiwo of a 
Pedipalp (Phrynid) belong to the first and second abdominal 
appendages. The author gives no further account of the 
development of the lung-books, but mei*ely states that it does 
not differ from that in other Ai’achnids (p. 616). 
Schimkewitsch (:03, ;06) gives a more detailed account of 
the development of the lung-books in Thelyphonns 
ca lid at us. According to him the lung-books are formed 
from pulmonary sacs or invaginations at the base of appen- 
dages, which are placed on the hind margins of the second 
and third abdominal somites. The lung-leaves arise as folds 
in the lower wall of this sac, and later on the leaves, which 
were formed in the sac, come to lie outside of it on the 
posterior side of the appendages so that the saccules then 
open to the outside instead of into the sac (fig. 46). Several 
sections of later stages of the lamellae are figured. 
Sophie l^ereyaslawzewa (:07), in a posthumous memoir, 
describes and figures some interesting stag-es in the develop- 
ment of the lung-books of a scorpion (Androc tonus orna- 
tus) from the material left by Kowalevsky and Schulgiii. 
