396 



EXPERIMENTAL FISH EMBRYOLOGY 



Fig. 4. Axial structures (I) induced from tJie extra-embryonic epithelium of a Fundulus egg by implanta- 

 tion of young dorsal lip into the edge of the blastoderm; drown 21-1/2 hours after operation. 



Fig. 5. Embryonic structures (I) induced in Fundulus by implantation of a dorsal lip material into extra- 

 embryonic epithelium; drawn 2-3/4 days after operation. E, ear. 



Fig. 6. Perch embryo (I) induced by dorsal lip implanted into extra -embryonic epithelium; drawn 1-1/2 

 days after operation. This embryo was probably a lateral hemi-embryo; somites were formed 

 on one side only. 



Figs. 7 and 8. Two stages in the development of a Fundulus embryo induced by the implantation of very 

 young dorsal lip into a very young gastrula; drawn at 18 hours and 3-1/4 days after operation. 

 The right part of the graft, which had been stained with Nile blue sulphate, failed to invaginate 

 and formed a knob (G) at the right side of the developing induced embryo; as a result the in- 

 duced embryo (I), although two ears were formed, was a lateral hemi-embryo with somites 

 present only on the left side. 



Fig. 9. Fundulus embryo (I) induced by a dorsal lip graft implanted into the edge of the blastoderm; 



drawn 3 days after operation. The ears and right fin of the induced embryo are formed posterior 

 to the corresponding structures in tlie primary embryo (P). 



Fig. 10. Head structures of Fundulus (I) induced by a dorsal lip graft which was originally implanted into 

 extra -embryonic epithelium but which shortly after implantation became incorporated into the 

 primary embryonic shield; drawn 3 days after operation. 



Fig. 1 1 . Fundulus embryo (I) induced by the implantation of very young dorsal lip; the graft was incor- 

 porated into the primary embryonic shield. Drawn 22 hours after operation. 



Fig. 12. Somites (I) induced by a dorsal lip graft implanted into the primary embr^'onic shield; 1 day 



after operation. The accessory somites persisted for 2 days and subsequently were absorbed into 

 the host; compare embryo shown in Fig. 6, where somites induced in an extra -embryonic region 

 exhibited a different segmentation from the host's. 



fig." 13. A dorsal lip graft implanted anteriorly in 



the embryonic shield was partially absorbed 

 into the forebrain, with the result that this 

 structure has wider walls than normal. 



Fig. 14. A graft of cells removed from a lateral port 

 of the shield formed brain (G) in the mesen- 

 cephalic region of the host. HOL, optic 

 lobes of host. 



Fig. 15. A perch embryo in which dorsal lip implanted 

 into the embryonic region was transformed to 

 brain; drawn 6 days after operation. 



(From Oppcnheimcr 1936: Jour. Exp. Zool. 72:409) 



