EXPERIMENTAL FISH EMBRYOLOGY 399 



DRAWINGS OF BLASTOMERE DESTRUCTION AND EXCISION EXPERIMENTS 



B. REMOVAL OF PARTS OF THE GERM RING : Stagea #10 to #15- 



The germ ring I3 so adherent to the underlying yolk that the suction proce- 

 dure nniat be used cautiously or the yolk will exude whereupon death follows. 



1. Use the window or decapsulation method, and suck out the ectoderm (only) 



of tne germ ring up to not more than 20$ of the ring. Concentrate on those 

 parts of the germ ring distant from the early shield. 



2. Suck out parts of the early neural keel (stage #15), with and without the 

 adjacent germ ring. (Nicholas and Oppenhelmer found that if 25^ of the 

 keel is removed, development ceases.) 



