Vitality and Organization of Protoplasm. 55 



formed by a mere conglomerate of cells, completely separated from one 

 another by membranes and having independent lives. There exist, on 

 the contrary, in the tissues and organs such numerous connections be- 

 tween equal and disparate cells, that it is entirely justifiable to regard 

 the body as a unitary mass of living substance, as a synplasm." Even 

 Haacke, an out and out aggregationist and mechanician, by admitting 

 in his "Gestaltung and Vererbung," 1893, p. 124, that "every cell of 

 the organism is directly or indirectly connected with all the rest by pro- 

 toplasmic bridges'' virtually acknowledges the unity of the living sub- 

 stance composing the organic individual. It would seem that zoolo- 

 gists are as much justified as botanists to conclude from the continuity 

 of the living substance : "the unity of the organic individual," in opposi- 

 tion to its formation ont of autonomous cells. But other stringent 

 proofs of the unity of the animal organism are at the command of zoolo- 

 gists. 



Eecent experiments on ontogenetic potentialities of fragments of egg- 

 plasm and on the extent and efficiency of regeneration in general, have 

 broken further decisive ground towards the establishment of the es- 

 sential unity of animal organization. Eoux, although himself an ag- 

 gregationist, has as early as 1885 drawn the logical conclusion that "if 

 the germ does not contain definitely preformed germinal particles, then 

 differentiation must be dependent on the influence of the whole of the 

 embryo upon its sundry parts.* Eoux's own pregnant experiment, per- 

 formed 1888, resulting in the formation of half -embryos, from one of 

 the two blastomeres, when the sister-blastomere had been killed, involved 

 unbeknown to him, the "influence of the whole of the embryo upon its 

 sundry parts," and it involved, moreover, irresistibly, the complete over- 

 throw of the cell-theory. For the two blastomeres proved by this de- 

 cisive experiment to be, not what according to tlie cell-theory they would 

 have to be, namely equal daughter-cells formed by the self-division of an 

 elementary mother-cell ; but, on the contrary, they proved to be the po- 

 tential embodiment of the complemental halves of one and the same 

 organism to be ontogenetically evolved. It follows that all further 

 stages of segmentation can not be anything in the remotest degree re- 

 sembling the multiplication by self-division of autonomous cellular 

 beings; but that they represent the visible segregation of strictly com- 

 plemental parts of a predetermined whole in the course of being evolved. 

 This is not a hypothetical assumption, but a positively observed fact. 



Pflueger's results gained by experime^jts with the eggs of frogs, pub- 

 lished in his Archiv 1883, and formulated in his theory of the "Isotropic 

 des Eiplasmas," led to similar conclusions. They proved that, though 

 the different constituent elements of the egg-plasm are made to change 

 their relative positions, a perfectly formed embryo is nevertheless pro- 

 duced. And, even if it is true as Born seems to have shown, that no 



*Einleitxing zu den Beitras'en der Entwicklungsmeclianic des Embryo. Zeit- 

 scrift fur Biologie, 1885. 



