CHORIO-ALLAXTOIC GRAFTS. 2Q3 



found that the optic cup of the amphibian embryo has groat 

 power of self-differentiation when transplanted to other parts of 

 the same or another eml >ryi , while the lens ectoderm is dependent 

 on contact with the optic cup for its development. The speci- 

 ficity of the ectoderm which forms the ! ries with the species 

 employed. Lewi-; PC 7 otes that the various parts of the cup 

 develop independently "in marked contra-t" to the lens which 

 will not form unle the optic cup is present. If brain also is 

 piv-ent , tht TV may r may not be an optic nerve developed. The 

 tissues -rrm to coniinuc t lu-ir own specific type of differentiation 

 independenl "t" one .mother. 



Tin- f.id that in ase 14.1 i where no brain ti ue i- pn-sent, 

 tin- optic ner\e i- also Kicking, while in case 10. /." i;, both 

 pn eems, th< -erve more than pa ini^ noti 



In the lir.-t meiit i< >n< , the point of fusion i>f the cut i 



the primordium i- definable. There is no indication of the optic 



n\ \\here in thi n. In case 9 A i. while tin 



-mall .iiiioimt i .1" br.iin ti--ue present, the po-itimi of the ojitic 

 iiciM- (.iniioi be found. It may be obliterated by the 14: 

 numbt-r t dr^nu-i :i\olutions in the retir i t.i|)ctuin 



adjoining tin I -e 19 E 13, however, bot h optic in i \ r 



and pi ( ti-n ai ilrtinitely located. The position of the optic 



nei\c i- tin- -.inn- .1- th.it of the optic stalk which connect- the 

 ic cup \\ith the brain in the early stages of de\ elopnieiit . 

 When thi- i- removed, the optic nerve fails to dc\dop. The 

 fibers oi i he < ell>, in-te.;d < !" finding exit by this path, .ire retained 

 in the -tr.itum opticiim. It would seem that the-e -trucuin - 

 we'll as the p.irt- of the retina and lenticular re^io- from \ 



delmite loc.n ion- in t he |>rimordium. 



The experiments show very definitely that the \ariou-; 

 the e\e | H iniordiiiin have the power of independent self-differenti- 

 ation to quite a remarkable extent. Thi- mnrlu-ion i- >tren-th- 

 encd l.ty the findings of Lewis, Spemann and other- for the amphib- 

 ian eye. The regulation of the part- to form a more or le-- ; 

 feet -tructun -'.ins, on the other hand, to be dependent on 

 vari< >u- mechanic.il factors involved in the experiment. 



