EXPERIMENTAL FISH EMBRYOLOGY 1|£1 



There is a quantitative decrease in regenerative or regulative capacity during early 

 development as revealed by the preceding operations. Nicholas and Oppenheimer, using 

 Fundalus, found no permanent damage up to the l6-cell stage of many of the operated forms. 

 "Up to this point the blastomeres may he regarded as totipotent so long as one-half of the 

 original content of the egg is left untouched." (Nicholas & Oppenheimer, 19^2.) Follow- 

 ing this stage there is rapid reduction in regulation, with progressive differentiation. 



RECORD OF ABLATION EXPERIMENTS ON LATER STAGES 



D. TRANSECTIONS OF THE SPINAL CORD OF MOTILE STAGES : (stage #25) 



The nerve cord is transected (without removal of any tissue) with a sharp 

 steel needle or iridectoiny scissors, avoiding injury to the notochord if possible. 

 The transections should be at different levels gind records should include descrip- 

 tion of the type of movement upon development to stage #26. Histological analysis 

 will determine the degree of damage and reconstitutlon. 



