296 



EYE FIELD OPERATIONS 



UPPER EYELID 

 CIUARY BODY 



EPIDERMIS 

 CUTIS 



SUSPENSORY LIGAMENT 



:OUS HUMOR 



TAL CAVITY 



C CAPSULE 

 LENS ) EPITHELIUM- 

 ( FIBRES 



NICTITATING MEMBRANE 

 LOWER EYELID 



f-OPTIC NERVE 



SCHEMATIC DIAGRAM THROUGH FROG'S EYE 



(Redrawn from Mangold 1931) 



"It might be wise to review Spemann's 1938 Silliman Lectures and 

 ponder on some of his statements of fact before proceeding to the cliaotic 

 condition through which the successive experiments liave led. Certaiidy 

 to Spemann there was a continuity in development which he rejoiced to 

 describe in oversimplified anthropomorphic terms. To him development 

 was a continuum which luid to be described in stepwise fashion. Tiiis was 

 for convenience only and not because he considered the embryo to be de- 

 veloping and differentiating through active and iiuictive periods of response. 

 His whole research career was founded on aski)ig the embryo simple ques- 

 tions which are experinicntally and intellectually possible of solution. " 



J. S. Nicholas 1960 



