64 



GROWTH AND MORPHOGENESIS 



f 



P-^' 



-^ 



A 



■s-v.. 



■•>■ 

 .-A 



Fig. 24. Disappearance of normal RNA gradient in centrifuged uncleaved egg 



of Xenopus; compare with Fig. 4. The main layers are, from top to bottom : 



pigment, fats, basophilic hyaloplasm, pigment and yolk. 



Fig. 25. Local accumulation of RNA in a region which will form a secondary 

 embryo in a centrifuged blastula (Unna staining). 



