534 THE ORIGIN OF VERTEBRATES 
Scaphaspis, 349 
Schwann, sheath of, 469 
Sclerotomes, 388 
Scorpion, brain, 54 
. branchial lamellae, 175 
5 development, 482 
os entochondrites, 377 
5 excretory organs, 397 
- eyes, 75 
io lung-books, 150, 170 
‘4 lymphatic glands, 423 
45 muscles, oblique, 278 
% 3 recti, 271 
35 5; respiration, 171 
5 4 veno-pericardial, 177 
+ muscular system, 247, 268, 269 
. nerves to Chelicere, 237 
iy olfactory organs, 220 
7 operculum of male, 189, 206, 212 
5 pecten, 359, 366, 371, 373, 374, 377 
5 under surface, 372 
uterus, 189, 202, 208, 204, 205, 212 
Sea- -sourptons. 25, 26, 27, 56, 150, 170, 191, 208, 221, 232, 235, 241, 849, 359 
Segmentation, beanshiouarte, 124 
- body-muscles in vertebrate, 388 
i eye-muscles, 248 
45 of head, double, 155, 157, 178, 234, 258, 411, 459 
bs of head-shield, 339 
history of cranial, 258 _ 
Searels branchial of Ammoceetes, 161, 178, 186 ; 
‘ hyoid, in Ammoccetes, double, 186, 201, 267, 300 
i innervation of branchial, 151 
6 first mesosomatic, in Limulus and its allies, 188 
3 mesosomatic, of Eurypterus, 192 
ii prosomatic of Limulus and its allies, 283, 249 
33 Ammoceetes, 286 
5 of gofnal region of Vertebrates, 388 
+f of trigeminal nerve-group, 257, 279 
tubular muscles of hyoid, 299 
Serine: -organs of Amphioxus, 34 
5 branchial, of Limulus, 359, 360 
5 lateral, of Annelids, 357, 367 
3 lateral-line system, 356, 411, 470 
Serum, 492 
Significance of the optic diverticula, 102 
Silurus, 488 
Sinus, longitudinal venous, of Limulus, 176, 312, 451 
» ‘rhomboidal of bird, 46 
Skeleton, Ammoceetes, 126, 296, 335 
9 ‘4 branchial, 126, 126 
5 Pa basi-cranial, 132 
3 a muco-cartilaginous, 291, 296, 330, 331 
