164 THE ORIGIN OF VERTEBRATES 
segmental nerve, which supplies its own branchial muscles and no 
others with motor fibres, and sends sensory fibres to the general surface 
of each appendage, as also to the special sense-organs in the shape 
of the epithelial pits (S., Fig. 65) arranged along the free edges of 
Fig, 65.—SEcTIonN THROUGH BRaNncHIAL AP- 
PENDAGE OF AMMOCGTES. 
br. cart., branchial cartilage; v. b7., branchial 
vein; a. br., branchial artery; b.s., blood- 
spaces; p., pigment; S., sense-organ; c., cili- 
ated band; £., I., external and internal 
borders; m. add., adductor muscle; m.c.s., 
striated constrictor muscle; m.c.t., tubular 
constrictor muscle; m. and m.v., muscles 
of valve. 
Fic. 66.—SEcTION THROUGH BRAN- 
CHIAL APPENDAGE OF LIMULUS. 
br. cart., branchial cartilage; 
v.br., branchial vein; b.s., blood- 
spaces formed by branchial artery ; 
P., pigment; m, posterior enta- 
pophysio-branchial muscle; mz, 
anterior entapophysio-branchial 
muscle; m;, external branchial 
muscle, 
the diaphragms ; each of these nerves possesses its own ganglion— 
the epibranchial ganglion. 
The work of Miss Alcock has shown that the segmental branchial 
nerve supplies solely and absolutely such an appendage or branchial 
