EXPLANATION OF PLATES 34 — 42. 



metapterygium). fr. cartilaginous fin-rays. pg. pectoral girdle in transverse section. 

 fo. foramen in pectoral girdle, pc. epithelium of peritoneal cavity. 



Fig. 7. Transverse section through the pectoral fin of a Scylliuni embryo of stage 

 P, magnified 50 diameters, bp. basipterygium. br. cartilaginous fin-ray. m. muscle. 

 hf. homy fibres. 



Fig. S. Pectoral fin of an embryo of Scylliiim stdlare, magnified 16 diameters. 

 mp. metapterygium (basipterygium of earlier stage), me.p. rudiment of future pro- 

 and mesopterygium. sc. cut surface of a scapular process, cr. coracoid process. 

 fr. foramen, hf, horny fibres. 



Fig. 9. Skeleton of the pectoral fin and part of pectoral girdle of a nearly ripe 

 embryo of Scyllium stellare, magnified 10 diameters, tnp. meiapterygium. incs. 

 mesopterygium. pp. propterygium. cr. coracoid process. 



EXPLANATION OF PLATES 34—42. (XXII. p. 738.) 



List of Reference Letters. 



a. Anus, a b. Air-bladder, a b'. Aperture of air-bladder into throat, a c. An- 

 terior commissure, af. Anal fin. al. Alimentary canal, ao. Aorta, ar. Artery. 

 au. Auditory pit. b. Brain, be. Body-cavity, bd. Bile duct. bd'. Aperture of 

 bile duct into duodenum, bl. Coalesced portion of segmental ducts, forming urino- 

 genital bladder. bra. Branchial arches, brc. Branchial clefts, c. Pyloric cseca. 

 d. Apertures of ca:ca into duodenum. cb. Cerebellum. cdv. Cardinal vein. 

 ce. Cerebrum : in figs. 47 A and B, anterior lobe of cerebrum, ce'. Posterior lobe of 

 cerebrum, cf. Caudal fin. en. Centrum, cli. Choroidal fissure, crv. Circular 

 vein of vascular membrane of eye. csh. Cuticular sheath of notochord. cv. Caudal 

 vein. d. Duodenum, dc. Dorsal cartilage of neural arch. df. Dermal fin-rays. 

 dl. Dorsal lobe of caudal fin. dlf. Dorsal fin. t: Eye. ed. Epidermis, ep. Epi- 

 blast. fb. Fore-brain, fe. Pyriform bodies surrounding the zona radiata of the 

 ovxim, probably the remains of epithelial cells, gb. Gall-bladder, gd. Genital duct 

 gl. Glomerulus, gr. Genital ridge, h. Heart. /; a. Hremal arch. // b. Hind 

 brain, h c. Head-cavity, hp d. Hepatic duct, h m. Hyomandibular cleft. /; op. 

 Operculum, hy. Hypoblast ; in fig. 10, hyoid arch. hyl. Hyaloid membrane, i c 

 Intercalated cartilaginous elements of the neural arches, in. Infundibulum. h: Iris 

 is. Interspinous cartilage or bones, iv. Sub-intestinal vein. ivr. Intervertebral 

 ring of cartilage, k. Kidney. /. Lens. Ic. Longitudinal canal, formed by union of 

 the vasa efferentia. Un. Lobi inferiores. //. Ligamentum longitudinale superius. 

 Ir. Liver. It. Lateral line. ly. Lymphatic body in front of kidney, m. Mouth, 

 mb. Mid-brain, mc. Medullary cord. mel. Membrana elastica externa. nies. 

 Mesorchium. mn. Mandible, md. and mo. Medulla oblongata. ms. Mesoblast, 

 na. Neural arch. na'. Dorsal element of neural arch. iic. Notochord. nve. Net 

 work formed by vasa efferentia on inner face of testis, od. Oviduct, od'. Aperture 

 of oviduct into bladder, ol. Nasal pit or aperture, olf. Olfactory lobe. op. Optic 

 vesicle, opch. Optic chiasma. op I. Optic lobes, opth. Optic thalami. orep. 

 Oral epithelium, ov. Ovary, p. Pancreas, pc. Pericardium, pcf. Pectoral fin. 



B. IV. e 



