organisers: inducers of differentiation 



8s 



the skin in an abnormal position, or by grafting a piece of foreign 

 epidermis over the eye-cup in situ. In both cases, a lens is formed.^ 



L.n. 



Fig. 89 



Development of the lens in Bomhinator pachypus. a, Transverse section through 

 larva from which the presumptive eye-rudiment was removed at the early 

 neurula stage: result, no lens, b. Transverse section through larva from which 

 the optic vesicle was removed at the early tail-bud stage : result, small lentoid 

 thickening of epidermis (L.f.). L.n. normal lens of unoperated side. (From 

 Mangold, Ergehn. der Biol, vii, 193 1, after Spemann.) c, Enlarged view of 

 lentoid (also seen at Fr.L.) developed after eye-cup removal and rearing at 23° C. 

 N. nose; H. brain. (From von Ubisch, Zeitschr. Wiss. Zool. cxxiii, 1924.) 



^ Filatow, 1924, 1926. 



