LIST OF ILLUSTRATIONS XV 



FIG. PAGE 



191. Anterior portion of body of young transparent Amphioxus 396 



192. Anterior portion of the spinal cord of Amphioxus . . 396 



193. Median vertical section through the cerebral vesicle of 



Amphioxus 397 



194. Transverse section through the middle region of the spinal 



cord of Amphioxus ........ 398 



195. A nephridium of Amphioxus, belonging to the left side of 



the body 399 



196 Portion of a transverse section through the pharynx of 



Amphioxus, in order to show position of the excretory 

 tubule 400 



197 Ventral view of an Amphioxus dissected so as to show the 



reproductive organs ........ 401 



198 Diagrammatic transverse section of Amphioxus to show the 



relation of the excretory and genital organs . . . 402 



199. Side view of the anterior end of a larva of Ascidia. . 405 



200. Dorsal view of the anterior end of a larva of Ascidia . 405 



201. Diagrams showing the changes undergone by a larval 



Ascidian in its metamorphosis . . . . 406 



dona intestinalis . ....... 407 



View of Ciona intestinalis lying on its right side . . 409 



204. Two groups of individuals of Botryllus violaceus . . -410 



205. Dorsal view of a fully-grown specimen of the solitary form 



of Salpa democratica . . . . . . . 411 



206. Semi-diagrammatic view of left side of Salpa . . . 412 



207. Views of the brain of a Dogfish, Scyllium catulus, from 



various aspects . . . . . . . . 415 



208. Transverse section through the snout of a Dogfish, Scyllium 



canicula . 418 



209. Ear of Chimaera monstrosa ....... 419 



210. Section of an ampulla of the internal ear . . . . 420 



211. Transverse section through the head of an embryo Chick 



of the third day of incubation in order to show the 

 origin of the retina and lens of the eye . . . 421 



212. Diagram to illustrate the structure of the retina . . 423 



213. Diagram of the arterial system of the Dogfish, Scyllium . 432 



214. Diagram of the venous system of the Shark, Mustelus 



antarcticus . . . . . . . . . 435 



215. Dissection of the muscles of the eye of Scyllium canicula 436 



216. Diagrams illustrating the development of the excretory and 



reproductive systems in Craniata ..... 438 



217. Diagram of a transverse section through a hypothetical an- 



cestral Elasmobranch in order to show the origin of the 

 excretory and genital organs 441 



218. The Musk Lamprey, Petromyzon uiilderi, in the act of spawning 444 



