222 THE ORIGIN OF VERTEBRATES 
character is, of course, evident enough, for it is innervated by a pair of 
nerves, and these nerves, as ought to be the case, arise from the supra- 
cesophageal ganglia, In Galeodes it is a conspicuously paired antennx- 
like organ (Fig. 94). 
Croneberg has also shown that this rostrum, or camerostome, arises 
embryologically as a pair of appendages similar to the other append- 
ages. This last observation 
of Croneberg has been con- 
firmed by Brauer in 1894, 
who describes the origin of 
the upper lip, as he calls it, 
in very similar terms, with- 
out, however, referring to 
Croneberg’s paper. Crone- 
berg further shows that this 
foremost pair of antenn 
not only forms the so-called 
upper lip or camerostome, 
but also a lower lip, for 
from the basal part of the 
camerostome there projects 
on each side of the pharynx 
a dependent accessory por- 
tion, which in some cases 
JU f---v.c fuses in the middle line, and 
Fic. 94.—Dorsat View or Brain anp Came- forms, as it were, a lower lip. 
SHETOME OF CALRODER. The entosclerite belonging 
cam., camerostome; pr. ent., pre-oral entoscle- to this depen dent portion 5 
rite; J.J., dependent portion of camerostome ; 
ph., pharynx; al., alimentary canal; . op., apparently the post - oral 
median optic nerves; pl., plastron; vc, entosclerite of Lankester and 
ventral nerve chain; 2, 8, second and third Nise Beck 
oer At the base of the tubular 
passage formed by this modified first pair of antenne the true mouth 
is found opening directly into the dilated pharynx, the muscles 
of which enable the act of suction to be carried out. The narrow 
cesophagus leads out from the pharynx and is completely surrounded 
by the supra- and infra-cesophageal nerve masses. 
Huxley also describes the mouth of the scorpion in precisely the 
same position (of. 0, Fig. 96). 
