380 GERMINAL ORGANIZATION — • INDUCTION PHENOMENA 



Fig. 48. Effect of transpos- 

 ing the inner dorsal part of 

 the blastocoele floor in an 

 early Discoglossus gastrula 

 to the ventral part of this 

 same cavity (insets: the 

 blastocoele floor is seen 

 from above; 1,2: successive positions of the displaced material). In (A), this internal 

 translocation has been done to the left. A secondary embryo has been obtained there. The 

 graphic reconstruction shows the primary (I) and secondary systems (II) as seen from their 

 dorsal aspects. The anterior part of the nervous system of I has been omitted. The secondary 

 system is rather complex, except for eyes. In (B) the transfer has been done to the ventral 

 right part. The secondary induction (II) is limited to an acrencephalon (perhaps the whole 

 acromerit?) plus a small otocyst and a pair of ganglia. The primary embryo (I) is some- 

 what deficient. The reconstruction is seen from the ventral side of I. Its somites have been 

 omitted. Aud. -otocyst; Br. -brain; D. -dorsal; Ep. -epiphysis; Gg.-ganglio; M. -somites; 

 n.c.-notochord; Olf -olfactory placode; O. v.-optic vesicle; Pr.-pronephros; sp. c. -spinal 

 cord ; V. -ventral. Such operations reveal that appreciable factors of organization exist in the 

 yolky cells located in the dorsal part of the blastocoele floor, and that the dorso-marginal 

 field extends fairly deeply into this area. From Dalcq, 1940. 



