Fig. 13. Portion of posterior end of a blastoderm of stage B, shewing the formation of cells around the nuclei of the yolk.
Fig. 14. Section through part of a young Scyllium egg, about 1/15th of an inch in diameter.
nl. Protoplasmic network in yolk. zp. Zona pellucida. ch. Structureless chorion. fep. Follicular epithelium. x. Structureless membrane external to this.
EXPLANATION OF [PLATES 8] AND [9]. (X. p. 286.)
Complete List of Reference Letters.
a. Arteries of yolk sac (red). al. Alimentary cavity. alv. Alimentary vesicle at the posterior end of the alimentary canal. an. Point where anus will appear. auv. Auditory vesicle. bl. Blastoderm. ch. Notochord. es. Embryo-swelling. h. Head. ht. Heart. m. Mouth. mg. Medullary groove. mp. Muscle-plate or protovertebra. op. Eye. sc. Segmentation cavity. sos. Somatic stalk. ts. Tail-swelling. v. Veins of yolk sac (blue). vc. Visceral cleft. I. vc. 1st visceral cleft. x. Portion of blastoderm outside the arterial circle in which no blood-vessels are present. yk. Yolk.
Fig. A. Surface view of blastoderm of Pristiurus hardened in chromic acid.
Fig. B. Surface view of fresh blastoderm of Pristiurus.