THE ORGANIZER 



201 



Fig. 4 

 A 



Explantation of dorsolateral and lateral blastoporal 

 lips; at extreme right the explants (enlarged) after 

 16 hours of culture. 



B. Insertion of strips of presumptive ectoderm (ec. im. ) 

 into slits made through the lateral and ventrolateral 

 marginal zones. 



C. Ring embryo resulting from the foregoing operation, 

 bp.gr., blastoporal groove; ec.im., presumptive 

 ectodermal implant; en., presumptive entoderm; 

 nt, , neural tissue; pr. , presumptive chorda projec- 

 tion; vs., vital-stain mark. 



Fig. 5: 



A. B. Transplantation of dorsal lip (dl. ) from one egg 

 (A) into presumptive ectodermal region of another 

 egg (B). 



C. The implant has developed a blastoporal pocket 

 (bp. ) on one side of the presumptive chordal pro- 

 jection (pr. ), and a patch of neural tissue (nt. ) 

 on the opposite side. 



D. Implantation of two dorsal lips (dl. ) into the 

 ventrolateral marginal zones. 



E. Embryo resulting from the foregoing operation 

 (D, above), nt. , primary neural plate: nt. . and 

 nt. , secondary' neural plates. See figure 5, 

 plate 7, for cross section, 



(Schechtman: 1942 Univ. Calif. Pub. Zool. 51:1) 



Fig. 6: 



A.C.E. Implantation of strips of presumptive ecto- 

 derm into slits cut through the marginal zone at 

 various distances from the dorsal lip. 



B.D. F. Neurulae resulting from the foregoing opera- 

 tions, A, C, E, respectively, ec.im., ectodermal 

 implant; nt. , neural plate; pr. , projection. 



