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 



m.add 



v br.cart 



m, : 



m. 



m.v 



Fig. 65. — Section through Branchial Ap- 

 pendage of Ammoccetes. 



br. cart., branchial cartilage; v. br., branchial 

 vein; a. br., branchial artery; b.s., blood- 

 spaces ; p., pigment ; 8., sense-organ; c, cili- 

 ated band; E., 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. 



br.cart. 



Fig. 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 ; nti, posterior enta- 

 pophysio-branchial muscle ; m„, 

 anterior entapophysio-branchial 

 muscle ; w 3 , 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 



