886 THE ARACHNOIDAE. $ 318 
§ 313. 
The Lungs of the Arachnoidae consist of round sacs situated near the 
lower surface of the abdomen and communicating, externally, by transverse 
fissures. Their internal surface has numerous thin solid lamellae, triangu- 
lar or rhomboidal, and connected together like the leaves of a book. By 
reflected light these lamellae have the same silvery lustre as the tracheae, 
although, seen by direct light, they appear of a deep-violet, nearly black 
color. Each of these is formed by a membranous fold, between the two 
leaves of which the air enters from the general cavity of the lung and is 
divided into very minute portions. No traces of blood-vessels have been 
found in these Pulmonary lamellae, It is therefore very probable that the 
blood of the pulmonary arteries is effused into the parts surrounding the 
lungs, and in this way bathes the lamellae.” 
With the Scorpionidae, the four anterior segments have, each, on their 
under surface, a pair of stigmata. These animals have eight pulmonary 
sacs, in each of which there are twenty fan-shaped lamellae.” The genus 
Phrynus has only two pairs of pulmonary sacs, the stigmata of which are 
placed between the first and second, and the second and third abdominal 
segments. But each sac has eighty lamellae. With the Araneae, there 
are only two lungs occupying the base of the abdomen. The number of 
their lamellae is considerably less than in the preceding groups. But with 
the Mygalidae only, there is a second pair of lungs directly behind the first. 
The place occupied by these organs, is indicated, with the Araneae, by a 
triangular horny plate, at the posterior border of which is a stigma. 
1 These organs, with which no motions have been 
discovered, have been called Branchiae by many 
Zootomists. But. the name of Lungs is very ap- 
propriate since the respiration is aérial and not 
aquatic. 
2 For the lungs of the Scorpionidae, see Meckel, 
‘Transat. of Legons d. Anat. comp. of Cuvier, Th. 
IV. p. 291; Treviranus, Bau d. Arach. p. 7, Taf. 
I., and Beobacht. aus d. Physiol. p. 25, fig. 40-42 ; 
Miller, Isis, 1828, p. 708, Taf. X. fig. 1-3, and in 
Meckel’s Arch. loc. cit. p. 39, Taf. IT. fig. 11-13. 
Miller has very correctly, and in the above-men- 
tioned manner, understood this respiratory appara- 
tus, -while, on the other hand, Treviranus ind 
other anatomists, think that the air, instead of 
entering between the leaves of the pulmonary 
lamellae, passes over their external surface, and 
that the blood penetrates between the two plates 
composing the leaves. Newport (Philos. Trans- 
ker’s Zeitsch. 1849, I. p. 246) who, contrary to 
Blanchard, advances the view that these organs 
are only a form of tracheae, infra-formed, and 
which are without the spiral filament, because 
their simple, unbranched condition does not re- 
quire, like the ramose tracheae, a spring-like 
structure, to prevent them from collapsing. This 
act. 1843, p. 295, Pl. XIV.) is probably mistaken in 
saying that unnucleated cells and a very fine 
capillary net-work exist between these plates, and 
that the net-work arises from a branch of the pul- 
monary artery situated on the free border of each 
lamella, 
3 See Van der Hoeven, Tijdsch. loc. cit. 
+ 4The lungs of the Araneae have been studied 
by Meckel (Translat. Lecons d’Anat. comp. of 
Cuvier, loc. cit. p. 290), Treviranus (Bau d. 
Arachn. p. 24, Taf. II. and Beobacht. &c. p. 29, fig. 
43-47), Gaede, Nov. Act. Nat. Cur, XI. p. 335, 
(Mygale) ; but especially by Miller (Isis, 1828, p. 
709, Taf. X. fig. 4-6). See also Menge, loc. cit. 
p. 21, Taf. I. fig. 6-9. I am unable to say by 
what means the blood returns to the heart, whether 
by a direct course, or, more or less circuitously 
through the interstices of the parenchyma, for 
there are no veins, 
view put forth together with the general doctrine 
that the pulmonary sacs of the Arachnoidae are, 
likewise, but modifications of the tracheal type, 
has many facts deserving the attention of anato- 
mists, and especially the developmental relations 
of the spiral thread as observed in the embryos of 
these animals. — Ep. 
