112 BIOLOGICAL LECTURES. 



be a matter of quite secondary importance. As the nephro- 

 stome is not the result of cell-formation, but exists as such 

 before division into cells, so the organism exists before cleavage 

 sets in, and persists throughout every stage of cell-multipli- 

 cation. Continuity of organization does not of course mean 

 preformed organs, it means only that a definite structural 

 foundation must be taken as the starting-point of each organ- 

 ism, and that the organism is not multiplied by cell-division, 

 but rather continued as an individuality through all stages of 

 transformation and sub-division into cells. 



We have long been aware that the cell could not be taken as 

 the ultimate unit of life, and every notable effort to account for 

 heredity has led to the postulation of primary elements in com- 

 parison with which the* cells appear as complex organisms. 

 Since Ernst Briicke first contended for the organization of the 

 cell in 1861, and the existence of "smallest parts" as the basis 

 of this organization, we have seen similar ideas reappear in the 

 "physiological units" of Herbert Spencer, the "gemmules" of 

 Darwin, the "micellae " of Nageli, the "plastidules " of Elsberg 

 and Haeckel, the " inotagmata " of Th. Engelmann, the "pan- 

 gens" of de Vries, the "plasomes" of Wiesner, the "idioblasts" 

 of Oscar Hertwig, and the " biophores " of Weismann. 



After the discovery of cell-division as the law of cell-forma- 

 tion, and after the scheme of the cell set up by Schleiden and 

 Schwann had been revised and reduced to essentialities by 

 Leydig, Max Schultze, and others, the next great step forward 

 in the cell-doctrine must be credited to Briicke, who, seeing that 

 the phenomena of life could not be referred to a structureless 

 substance, declared for the organization of the cell in words 

 that were scarcely less than revolutionary. 



" We must therefore," says Briicke, ascribe to living cells, in addi- 

 tion to the molecular structure of the organic compounds which they 

 contain, still another, and otherwise complicated, structure ; and this 

 it is that we designate by the name organization." 



Further, in his own words : " Wir miissen in dcr Zelle immer einen 

 kleinen Thierleib sehen, und diirfen die Analogien, welche zwischen ihr 

 und den kleinsten Thierformen existiren, niemals aus den Augen lassen" 

 (Elementarorganismen, p. 387.) 



