314 Development of the Cell and [BOOKII. 



from new points of view, gave it the name of protoplasm which 

 it still bears, and showed that it is this substance, and not the 

 proper cell-sap, which carries out the movement of rotation 

 and circulation in cells discovered by Corti in the previous 

 century, and again observed by Treviranus in 1811. The 

 Algae proved highly instructive in the study of this remarkable 

 substance also. The swarm-spores of Algae and Fungi ob- 

 served by Alexander Braun, Thuret, Nageli, Pringsheim, and 

 De Bary showed that protoplasm is not dependent on the cell- 

 membrane for its vitality, that by virtue of its own internal 

 powers it can alter its form, and even move in space. In 1855 

 Unger in his ' Lehrbuch ' pointed out the resemblance of this 

 substance to the matter known as sarcode in the lower forms 

 of animals, a resemblance brought out more plainly in 1859, 

 when De Bary's studies of the Myxomycetes proved that the 

 substance of these forms was protoplasm, which continues to 

 live for a considerable time, and often in large masses, before 

 it forms cell-membranes. Zootomists now began to take an 

 interest in these results of botanical research ; Max Schulze 

 (1863), Briicke, and Kiihne studied animal and vegetable 

 protoplasm, and the conviction gained ground more and more 

 in the years from 1860 to 1870 that protoplasm is the imme- 

 diate principle of vegetable and animal life. This discovery is 

 one of the most important results of research in modern 

 natural science. 



Not less important were the results obtained from the study 

 of the rest of the organised contents of cells ; von Mohl 

 proved that chlorophyll-corpuscles, the most considerable 

 organs of nutrition in the plant, are formed of protoplasm, 

 and Theodor Hartig, though his cell-theory was a mistake, did 

 good service by his discovery of aleurone-grains in seeds and 

 of the crystalloids which sometimes occur in the grains, 

 and which are also formed of protoplasm and renewed from 

 protoplasm. Radikofer, Nageli, and others added to our 

 knowledge of the form and chemical composition of these 



