OR IGIN OF AMPHIBIAN PIGMENT 



265 



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

 where in the lateral helly region, far removed from the host neural folds. The 

 emhryo should lie on its side in a Permoplast or paraffin depression deep enough 

 so that the helly ectoderm is flush with the surface of the Permoplast. 



2. Excise the neural fold of the right side from a similar emhryo of stage #15 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 (Briicke) 

 for 30 minutes without di sturhance . 



5. Transfer the embryo by means of wide-mouthed pipette to Growing Medium at iS'-'C. 

 or less for recovery and development. 



Eecently (19^5) Twitty rotated the neural crest and adjacent somite material with 

 interesting results (see accompanying figures). This operation should be attempted but 

 might be varied in respect to position on the host. If the somites and crest are re- 

 versed, it would be significant to make the l80° rotation at the level of the hind- or 

 forelimb to determine not only the alteration in pigment pattern but also in the muscular 

 control of the adjacent appendage. 





Fig. 2. Dorsal view of Trlturus torosus larva showing tMe transverse strands 

 which connect the paired bands of melanophores located on the spinal 

 cord. 



Fig. 3. (a) Extirpation of neural (trunk) folds. 



(b) Closure of "crestless" neural tube. 



(c) Block of tissue excised and grafted upside down In substitution 

 of the somites of another embryo (d & e) . 



(d) Diagram of transplant In host (d.m.s. - dorsal margin of myotome) 



(e) Inverted somites and neural crest in host. 



(f) Modified distribution of melanoDhores in host. 



V. C. Twitty, I9k^: Jour. Exp. Zool. 100:li^l. 



