264 SCIENTIFIC THOUGHT. 



Morphologically the microscopic examination of animal 

 and vegetable tissues had thus led not to a clearer defini- 

 tion of the great differences which exist in the forms and 

 structures of the larger and the full-grown organisms, but 

 rather to a conviction of their intrinsic and essential 

 sameness. These differences could not be explained in 

 the purely morphological manner in which Haiiy had 

 shown how to trace the difference of crystalline forms 

 to the shapes and configuration of the " molecules in- 

 te'grantes." The diversity of forms had to be traced to 

 48. processes of growth or development i.e., the purely 

 to the study morphological examination led on to the developmental 

 ment. or g ene ti c study of organic forms. And this was. made 

 still more evident when the microscopic examination 

 revealed yet other and more important elements in 

 the composition of organic structures, elements which 

 were seemingly quite shapeless or amorphous. The 

 skeleton, which had so long seemed to contain the key 

 to the understanding of organic forms, the framework of 

 the plant structure, the cell-walls and partitions, with 

 all their geometric figures and arrangements, turned out 

 to be of quite secondary importance compared with the 

 cell contents, the substance called in animals by Dujardin 

 sarcode, and in vegetables by Von Mohl protoplasm, and 

 with the nucleus or cell-kernel, which had been discovered 

 by Robert Brown. 1 Accordingly great interest attached 



sional basis for physical astronomy. 

 Both generalisations involve un- 

 solved problems, with the difference 

 that the formulation of the cellular 

 theory is not as precise as that of 

 gravitation. 



1 Both the discovery of the nucleus 

 by Robert Brown and that of the 



cell contents by Dujardin preceded 

 the enunciation of the cellular 

 theory. Brown's discovery was re- 

 ferred to both by Schleiden and 

 Schwann. In fact, Brown's re- 

 searches were much better known 

 and followed up in Germany than 

 in England. His papers were trans- 



