Vitality and Organization of Protoplasm. 7 



from what is actually witnessed as taking place in ontogenetic evolu- 

 tion. For it is seen to start from a singile cellular being, the germ-cell, 

 which divides into two "daughter-cells ;" these again divide, and' so on 

 and on, until by means of such successive self-divisions the vast cell- 

 aggregate is formed, which constitutes the complex multicellular organ- 

 ism. Microscopically the complex adult organism appears to be thus 

 composed of a countless number of elementary units, all the lineal off- 

 spring of the one parental germ-cell. 



It is upon these plainly visible facts that the cell-theory is principally 

 grounded. And its tenets seem not only ontogenetically evident, but ap- 

 pear to be, moreover, confirmed by the existence of colonial forms, con- 

 stituted by a number of more or less closely united unicellular beicgs, 

 such as enter, for instance, in the formation of Volvox and Magisphoera. 

 Some of these colonies bear a striking resemblance to the blastula stage 

 of Metozoa, and strongly suggest the formation of these by union of 

 similar unicellular beings. On the strength of such manifest evidence 

 the complex organism of plants and animals was declared to be, not 

 really the unitary being seen as such by unaided vision; but to be, on 

 the contrary, a populous commonwealth composed of a multitude of 

 autonomous elementary individuals, busily dividing among themselves 

 the divers ontogenetic and physiological labors, which result in the com- 

 plex structure, and the harmonized vital functions of the vast cell- 

 aggregate they constitute. This sociological interpretation of the con- 

 stitution of the complex organism was elaborated by Yirchow, Haeckel 

 and others, and was generally accepted as a fundamental tenet of biologj^ 



Though, even with the assistance of sociological analogies, it is ration- 

 ally inconceivable how the unconscious co-operation of numberless ele- 

 mentary beings can result in the ontogenetic reproduction of the strictly 

 predctennined, diversely constituted structures of an organic being, 

 itself infinitely more complex and potent than any of the constituent 

 cells; though, as conceived by the cell-theory, evolution of the adult 

 organism through self-division of an elementary germ-cell, and its 

 cellular progeny, is utterly incomprehensible, the cell-theory — seemingly 

 enforced by visible demonstration — became notwithstanding a generally 

 accepted doctrine, guiding biological research. 



It follows from its acceptance, that all vital efficiencies reside exclu- 

 sively in the sundry discrete cellular beings, as autonomous units. And 

 as ontogenetic evolution starts from one single such fertilized or un- 

 fertilized autonomous being, the task thus given was to discover what 

 endowments of the reproductive cell and its progeny lead to the divers- 

 ified development ultimately represented by the manifoldly constituted 

 tissues of the adult organism. How, then, does an epithelial cell, a 

 muscle cell, a nerve cell, and all other varieties of cells ; how do they 

 come to be potentially represented in the germ-cell? And how does 

 this minute, morphologically all but undifferentiated cellular being man- 

 age to evolve the huge structually differentiated form of the adult 

 organism ? 



R Yl :33| 



