568 CLASS IX. 
(Telephonus), or lying side by side form an abdominal cord with- 
out ganglia, as in the spiders. A chain of ganglia, as in most 
insects, is found in Zurdigrada, in Pycnogonida', and in Scorpio 
alone. In the Pycnogonida, the four ganglia, forming the row, le 
close together, without connecting cords, just as SWAMMERDAM has 
figured the nervous system in Pediculus (see above, p. 301). In 
Scorpio, on the contrary, they lie, seven in number, at considerable 
distances apart, and are connected by two strings”. Above, and 
commonly close upon the thoracic ganglion, is placed a ganglion 
which may be considered as cerebral ganglion; in very simply 
organised arachnids it is seen as a simple commissure on the ceso- 
phagus; in others it is oblong and formed of two small parts, 
mostly conical or pear-shaped, lying side by side. From it arise 
the nerves of the mandibles and of the eyes. Between this cerebral 
ganglion and the thoracic ganglion, there is always an opening, 
mostly very narrow, for the passage of the cesophagus, which is 
surrounded on each side by the nervous connexion of the two gan- 
glia. That the first ganglion is smaller than the second, and not 
broad, as in most insects, depends, without doubt, principally upon 
the absence of the compound eyes, whose nerves, in insects, have 
such a large development. Interesting also is the exceptional form 
of the nervous system in Phalangiuwm, where the nerves proceeding 
from the thoracic ganglion form eight ganglia in their course, four on 
each side, not behind one another in a row, but at different heights, 
dispersed on each side of the body, and distant from each other. 
Traces of a distinct nervous system for the intestines, of that 
system which we indicated above, in insects, as answering to the 
1 QUATREFAGES Ann. des Sc. nat. 3ieme Série, Iv. 1845. Zoologie, p. 77, Pl. 1. 
and II. 
2 TREVIRANUS Ueb. d. inn. Baw der Arachn. s. 14—16, Tab. I. fig. 13, and espe- 
cially Zeitschr. fiir Physiol. Iv. 1831. s. 89—97, Taf. vi. and the elaborate fig. of 
Neweort Phil. Trans. 1843, Part 1. Pl. x11. That the nervous system in Phrynus 
and Telephonus is formed not after the type of the scorpions, but of the spiders, was 
announced by me in the Z%jdschr. von Nat. Gesch. en Physiol. 1X. 1842, bl. 75, and xX. 
1843, bl. 369, 370. In Zelephonus, at least, it would be difficult to have anticipated 
this, and it is also in contradiction to the, rules, already contradicted indeed by other 
instances, which StrAuS DuRcKHEIM formerly laid down for the form of the nervous 
system of articulate animals. Consid. gén. s. VAnat. comp. des Ani. art. pp. 364, 365, 
371. 
3 TREVIRANUS Verm. Schr. 1. s. 38, 39, Tab. Iv. fig. 24, TuLK 1.1. p. 325, Pl. v. 
fig, 31. 
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