224 



REGENERATION 



Roux interprets Hertwig's results as due, to the sudden partial 

 post-generation of a part of the injured half of the egg. He thinks 

 that a half-embryo had first developed, and then to this there has been 



B 



FIG. 63. A. After Wetzel. Section through an egg (blastula stage) reversed at two-celled stage. 



B. After Schultze. Double embryo, from reversed two-celled stage, united ventrally. 



C, C 1 . Two views of another double embryo (united dorsally). C 2 . Cross-section through 

 last. D. After Wetzel. Double embryo united laterally. Z? 1 . Section through same. 



