Mtaliiif and Organization of FrotopJasm. 69 



such projection or pseudoiwdium steadily maintained, it clearly repre- 

 sents a bipolar and bilateral organism. How then does it happen that 

 in its higher stages of development this unitary bilateral constitution of 

 the living substance becomes divided during ontogenetic evolution into 

 two imilateral, but still interdependent halves? Here one is led to 

 assume, that in the course of phyletic elaboration the two lateral halves 

 of the living substance, though composing a continuous whole, have each 

 undergone more or less independent structural development, having 

 necessarily been separately, but under the same conditions, exposed to 

 the same stimulating influences of the medium, with which they have 

 stood, and are still standing in a relation of functional interaction. The 

 separate structural elaboration of each unilateral half has here evidently 

 come to constitute the most fundamental organic differentiation re- 

 tained in the chemical organization of the germ-plasm, expressing itself 

 ontogenetically in the segregation of the two first blastomeres, of which 

 each possesses then separately the power of further self-differentiation. 

 Bichat already recognized the bilateral duplication of organs as the 

 essential characteristic of what he called the animal life, which is the 

 life of the dynamical outside relations structurally embodied in the 

 ectodermic organs. Numerous observations and experiments prove that 

 the germ-plasm is bilaterally organized even before fertilization. 

 Watase found that the egg of the Loligo pealii discloses already before 

 fertilization a bilaterally symmetrical arrangement of its substance, 

 which determines the direction of the first segmentation, and the axis 

 of the embryo. The plasm of the egg of most insects is visibly bilat- 

 erally arranged. In annilides and mollusks the egg-plasm has like- 

 wise before fertilization a visible bilateral arrangement, which deter- 

 mines the direction of the first segmentation. Driesch showed by ex- 

 periments with the eggs of Echinus that they possess a bilateral structure 

 before fertilization, which after fertilization determined the direction of 

 the segmentation, and which in consequence is not due to the influence 

 of the spermatozoon as had been asserted by some investigators. R. 

 Hertwig, Morgan, Loeb and others by inducing through chemical means 



] unfertilized eggs to undergo normal evolution, proved thereby the orig- 



; inal bilateral structure of the egg-plasm. 



It is of paramount importance, as already stated, to recognize that 

 the first two blastomeres can nowise be regarded as the autonomous off- 

 spring of a self-dividing elementary organism, as demanded by the cell- 

 theory. Self-division produces here no equal sister-cells; equal to each 

 other, and equal to the mother-cell. On the contrary, self-division 

 divides here a whole into two complemental halves, each representing 

 only one lateral half of the "germ-cell" in a somewhat more advanced 

 stage of ontogenetic evolution. They each possess laterally con'espond- 

 ing ontogenetic potentialities, representing complemental halves of the 

 organism to be reproduced. The two primary blastomeres segregated 

 during ontogenetic evolution from an undivided whole, are destined 

 conjointly to reproduce in the course of ontogeny by one and the same 



