Further Examination of the Cell-Theory ^OS 



segment. ... I shook the germs rather violently during 

 the two-cell stage, and in several instances I succeeded in 

 killing one of the blastomeres, while the other one was not 

 damaged, or in separating the two blastomeres from one 

 another. 



"Let us now follow the development of the isolated sur- 

 viving cell. It went through cleavage just as it would have 

 done in contact with its sister-cell, and there occurred cleav- 

 age stages which were just half of the normal ones The 

 stage, for instance, which corresponded to the normal six- 

 teen-cell stage . . . showed two micromercs, two macromeres 

 and four cells of medium size, exactly as if a normal sixteen- 

 cell stage had been cut in two ; and the form of the whole was 

 that of a hemisphere. So far there was no divergence from 

 Roux's results. ... 



"I now noticed on the evening of the first day of the ex- 

 periment, when the half-germ was composed of about two 

 hundred elements, that the margin of the hemispherical germ 

 bent together a little, as if it were about to form a whole 

 sphere of smaller size, and, indeed the next morning a whole 

 diminutive blastula was swimming about. I was so much 

 convinced that I should get Roux's morphological result in 

 all its features that, even in spite of this wliole blastula, I 

 now expected that the next morning would reveal to me the 

 half-organisation of my subject once more. . . . But things 

 turned out as they were bound to do and not as I had 

 expected; there was a typically whole gastrula on my dish 

 the next morning, differing only by its small size from a 

 normal one; and this small but whole gastrula was followed 

 by a whole and typical small pluteus-larva. 



"That was just the opposite of Roux's result; one of the 

 first two blastomeres had undergone a half-cleavage as in 

 his case, but then it had become a whole organism by a sim- 

 ple process of rearrangement of its material, witliout any- 

 thing that resembled regeneration, in the sense of a comple- 



