SALINE SOLUTION 

 PRESUMPTIVE EYE 



UNDIFFERENTIATED 

 ECTODERM 



PRESUMPTIVE VALUE = EYE 



Fig. 32. A test for the potencies of the presumptive eye of the early gastrula, 

 with some of the results. A region of the early gastrula, at lower left, is stained 

 and found to develop into the eye, lower right. The presumptive eye is cut 

 out and transplanted to region 1, region 2, and region 3, of an older embryo. 

 In region 1 the presumptive eye develops into epidermis, brain, nasal placode, 

 and eye (upper left). Presumptive eye placed in region 2 forms otocyst, gills, 

 brain, and cartilage (upper right). Finally, in region 3, somites, notochord, 

 pronephnc duct, and spinal cord develop out of tissue which normally forms 

 eye (right center). If the presumptive eye is placed in saline solution it forms 

 a ball of undifferentiated ectoderm. 



