U02 



EXPERIMENTAL FISH EMBRYOLOGY 



RECORD OF NERVE COED TRANSECTION EXPERIMENTS 



DISCUSSION : 



With the Increaalng physiological complexity of the embryo there Is a decrease In the 

 regulative capacity, noted first at the l6-cell stage. When as much as 50^ of the proto- 

 plasmic material of the l6-cell stage Is removed In Pundulus (Nicholas & Oppenhelmer, 

 19^+2 ) defects appear and few of the fish gastrulate, hut the same proportion of protoplas- 

 mic material can be removed at the previous (8-cell) stage and this will be followed by 

 complete regulation. Following the l6-cell stage there Is a rapid drop In regulation, so 

 that at the blastula stage the embryo can tolerate a loss of not more than about 20^ of 

 the protoplasmic mass. 



( From Nicholas & Oppenhelmer I9U2 : Jour. Exp. Zool. 90:127) 



