CHORIO-ALLAXTOIC GRAFTS. 311 



of the embryo is very complex and for this reason an analysis 

 would be difficult. 



More n-cently Atterbury (1923) has transplanted the metan- 

 ephric "anlage" of the chick in the same way. The material 

 u-ed in the experiments was taken from seven day chicks 

 trail-planted to the membranes of chicks of the same age. The 

 primordium of the kidney consists of an ureteric channel with 

 < ral tubule- and metanephrogenous tissue at the time 

 trail-planted. Tin- differentiation obtained from such grafts 

 after variou- period >i\\ th was similar to that of the control 



melanephro-. The i-ohitcd metanephric primordium of the 

 chick embryo ha-, thu- the power of independent >clf-differen- 

 tiation as have the idied in this report. 



A genera] sun power of growth and differentiation 



of isolal ' was made as a preliminary to 



the piv-i -lit -tudy. The Drafts obtained from implant- of ci 



n and the primitive streak confirm 



the re-ult- t! M hakoft has obtained for the " bla-toderm in 



tot embryo. Cartilage, muscle, ncrvi >u- ti-- 



-ue, nepi ''ii- ti tie, and epidermis differentiate well. 

 Some of the im somitic region show \cry definite 



striation-. The cartilage suggests the form* it would have 

 Mimed in the normal embryo and the spinal nerve- ha\ rial 



iiunt iml segmentation in the cord. 



If the ii \\ith more or less extcn- m- 



pK I with the results obtained in the invi ion 



of the . 1 prim< .rdium of the single organ, i: r- that in 



both i he differentiation of the graft i- ilic 



nature, after a < eriain amount of physiological dilferentiat: 

 taken place in the transplanted. Thi> physiological dif- 



ntiationof the ct 11- of the organism h a tailed "i>roto- 



plaMiii. : ali/ation" by Child (1921). In ^peakin.^ of "-elf- 



di I tereiiti.it ion "in isolated parts of annelid and nmllu-k em In 

 he- 1. 120 "... protoplasmic specialization has advai 



so far that the regulatory reaction- to isolation of part- are 

 limited, and the behavior of the part after isolation i- th 

 much the saiiu- as before." Just when the speciali/ation of the 

 cells c>f the oixan primordium is est.ibli-hed in the chick embryo 

 matter re<|iiirin- further iiiv tion, though the n--ult- 



