184 Regeneration 



growth of the lens limited? The limitation in the 

 growth of organs is one of the most important problems 

 in growth and organ formation, though unfortunately 

 our knowledge of this topic is inadequate. 



7. The botanist J. Sachs was the first to definitely 

 state that in each species the ultimate size of a cell is a 

 constant, and that two individuals of the same species 

 but of different size differ in regard to the number, but 

 not in regard to the size of their cells. 1 Amelung, a 

 pupil of Sachs, determined the correctness of Sachs's 

 theory by actual counts. Sachs, in addition, recognized 

 that wherever there were large masses of protoplasm, 

 e. g., in siphoneae and other cceloblasts, many nuclei 

 were scattered throughout the protoplasm. He inferred 

 from this that "each nucleus is only able to gather 

 around itself and control a limited mass of protoplasm. ' ' 2 

 He points out that in the case of the animal egg the 

 reserve material — fat granules, proteins, and carbo- 

 hydrates — are partly transformed into the chromatin 

 substances of the nuclei, and that the cell division of the 

 egg results in the cells reaching a final size in which each 

 nucleus has gathered around itself that mass of proto- 

 plasm which it is able to control. Morgan 3 and 

 Driesch 4 tested and confirmed the idea of Sachs for 



1 v. Sachs, J., "Physiologische Notizen," vi., Flora, 1893. 

 'Ibid., ix., 425, Flora, 1895. 



a Morgan, T. H., Arch.f. Entwcklngsmech., 1895, ii., 81 ; 1901, xiii., 416; 

 1903, xvi., 117. 



<Driesch, H., Arch. f. Entwcklngsmech., 1898, vi., 198; 1900, x., 361. 



