266 



ORIGIN OF AMPHIBIAN PIGMENT 



3. Leave the embryo in Operating Medium until the wound closes over, then transfer it 

 to Growing Medium at about 15 -18 C. and allow it to develop. A single specimen in 

 a #2 Stender or finger bowl is best. 



This operation will have the more graphic results in the more highly pigmented Ambly- 

 stoma tigrinum or T. pyrrhogaster. 



HOMOPLASTIC NEURAL CREST TRANSPLANTATIONS 



Removal of neural crest material from the normal to a strange site should similarly 

 alter the final pigment pattern of the embryo. It is generally too drastic to make the 

 transplant on the same embryo, but comparable stages should be used or the donor ma- 

 terial may be taken from an embryo slightly older than the host. 



STAGE 15 



STAGE 17 



STAGE 18 



STAGE 18 



STAGE 



STAGE 



STAGE 32 



In Operating Medium, prepare a transplant site on the host embryo (stage #15) some- 

 where in the lateral belly region, far removed from the host neural folds. The em- 

 bryo should lie on its side in a Permoplast or paraffin depression deep enough so that 

 the belly ectoderm is flush with the surface of the Permoplast. 



Excise the neural fold of the right side from a similar embryo of stage # 1 5 or older, 

 and place it in the host wound, making the transfer on a needle point or by means of 

 the hair loop. Hold it in place with a piece of cover slip (Brucke) for 30 minutes 

 without disturbance. 



Transfer the embryo by means of wide-mouthed pipette to Growing Medium at 18°C. 

 or less for recovery and development. 



