62 SCIENCE AND PHILOSOPHY OF THE ORGANISM 



After first widening the circle of my observations by 

 showing that one of the first four blastomeres is capable 

 of performing a whole organogenesis, and that three of 

 the first four blastomeres together result in an absolutely 

 perfect organism, I went on to follow up separately one of 

 the two fundamental problems which had been suggested 

 by my first experiment : was there anything more to find 



FIG. 5. ILLUSTRATION OF EXPERIMENTS ON ECHINUS. 



aj and bj. Normal gastrula and normal pluteus. 



02 and bo- " Half "-gastrula and "half "-pluteus, that ought to result from one of the first 



two blastomeres, when isolated, according to the theory of " evolutio." 



03 and ba. The small but whole gastrula and pluteus that actually do result. 



out about the importance or unimportance of the single 

 nuclear divisions in morphogenesis ? * 



By raising the temperature of the medium or by diluting 

 the sea-water to a certain degree it proved at first to be 

 possible to alter in a rather fundamental way the type of 



1 Zeitschr. wiss, Zool. 55, 1892. 



