290 SOME PROBLEMS OF CELL-ORGANIZATION 



has been so widely accepted by botanists. In the meantime Darwin ^ 

 introduced a new element into the speculative edifice in his celebrated 

 hypothesis of pangenesis, where for the first time appear the two 

 assumptions of specific differences in the ultra-microscopic corpuscles 

 ("gemmules") and the power of self-propagation by division. Dar- 

 win did not, however, definitely maintain that protoplasm was actually 

 built of such bodies. The latter hypothesis was added by De Vries 

 ('89), who remodelled the theory of pangenesis on this assumption, 

 thus laying the basis for the theories of development which reached 

 their climax in the writings of Hertwig and Weismann. 



The views of Spencer and Darwin were based on purely theoretical 

 grounds derived from the general phenomena of growth and inheri- 

 tance.^ Those of Nageli, De Vries, Wiesner, Altmann, and others 

 were more directly based on the results of microscopical investigation. 

 The view was first suggested by Henle ('41), and at a later period 

 developed by Bechamp and Estor, by Maggi and especially by Alt- 

 mann, that the protoplasmic granules might be actually organic units 

 or bioblasts, capable of assimilation, growth, and division, and hence 

 to be regarded as elementary units of structure standing between the 

 cell and the ultimate molecules of living matter. By Altmann, espe- 

 cially, this view was pushed to an extreme limit, which lay far beyond 

 anything justified by the known facts; and the theory of genetic con- 

 tinuity expressed by Redi in the aphorism " oiniie viviiin ex vivo,'' 

 reduced by Virchow to '^ omnis cellula e cellnla,'" finally appears in 

 the writings of Altmann as '' omne granulum e granulo" !^ 



Altmann's premature generalization rested upon a very insecure 

 foundation and was received with just scepticism. Except in the case 

 of plastids, the division of the cytoplasmic granules was and still 

 remains a pure assumption, and furthermore many of Altmann's 

 "granules" (zymogen-granules of gland-cells, etc.) are undoubtedly 

 metaplasmic bodies.* Yet the beautiful discoveries of Schimper ('85) 

 and others on the origin of plastids in plant-cells give evidence that 

 these cells do in fact contain large numbers of bodies, other than the 

 nuclei, that possess the power of growth and division. The division 

 of the chlorophyll-bodies, observed long ago by Mohl, was shown by 

 Schmitz and Schimper to be their usual if not their only mode of ori- 

 gin ; and Schimper was able to trace them back to minute colourless 

 plastids, scarcely larger than " microsomes," that are present in large 

 numbers in the protoplasm of the embryonic cells and of the Q.^Z^ and 

 give rise not only to chlorophyll-bodies but also to the amyloplasts or 

 starch-formers and the chromoplasts or pigment-bodies. While it still 

 remains doubtful whether the plastids arise solely by division or also 



1 Variation of Anitnals and Plants, i86S. ^ cf. Introduction, p. 12. 



2 Die Elemeniarorganismen, Leipsic, 1894, p. 155. * Cf. Lazarus, '98. 



