INTRA -EMBRYONIC TRANSPLANTATIONS 



445 



Willier and Rawles have successlully transplantea neural crests between bird species 

 which exhibit radically different color patterns, and some which are white. They found 

 that the color pattern, in all cases, was due to the intrinsic genetic factors of the spe- 

 cific melanophores concerned, rather than to the feather structure. There was found to 

 be some slight modification of pigment expression of the melanophores by the host feather 

 germs. (See Willier 1941: Amer. Nat. 75:136 for review.) 



If the student has had success with transplantation of limb primordia, he might carry out 

 the following procedure which has as its aim the study of neural crests transplanted from 

 dark to light breeds of fowl. 



1. Donors consist of any dark breed (e. g. , Brown Leghorn, Barred Rock, New 

 Hampshire Red). They should be from 30 to 48 hours incubated (less than 15 

 somites) at the time of the excision of the neural crest. 



2. Hosts should be about 60 hours incubated. They should be White Leghorns. 



3. Under the usual aseptic conditions, make a longitudinal slit in the chorion, the 

 amnion, and finally at the base of the wing bud. Return the covered host to the 

 incubator. 



4. With a piece of Nile Blue Stained agar, stain for 10 minutes the head, anterior 

 to the otocyst. 



5. Ouickly excise the donor embryo from its yolk, remove all yolk, and strip a 

 piece of skin from the dorsal and dor so-lateral surface of the head (where it is 

 stained). The neural crest cells will be adherent to the undersurface of this 

 piece of skin. 



6. With pipette and sterile chick Ringer's transfer this neural crest material, to 

 the previously prepared slit at the base of the wing bud of the host. Gently 

 push it deeply into the opening and make certain that it sticks. 



7. Seal the window, and incubate the egg (without rotation for 48 hours) for at least 

 two weeks. If development seems normal, allow some hosts to go to hatching. 



1 day 2 diys 3 ola>s 



(0.0002 jiaml (O.OOigiaml fO.OSgiam^ 



■f days 

 (0.05 glim) 



5 days 

 (0 13 guml 



6 days 

 (0.2S giaml 



7 days 



(0.57 guml 



8 days 9 days 10 days 11 days 12 days 13 days !"( days 



(1.15 gumO 1 1.53 gumO ( 2.86 giaivisl OtSgtamsl (5.07 gjimil (7-37giiinsl (9.T» giimO 



15 days 16 days 17 days 18 days 19 days 20 days 21 days 



(I200gumsl (I5.98gum4l (l859gTamsl (21 83 gums) I25t2jiams) OO.SIgtamil (Hitched) 



DAILY CHANGES IN THE WEIGHT AND FORM OF THE 

 DEVELOPING CHICK EMBRYO (WHITE LEGHORN) 



Reprinted by permission of N. Y. State College of Agriculture 

 from Bulletin #205, Romanoff, 1931. 



