m< 







in 



; 



Further Examination of the Cell-Theory 205 



anura), served as the starting point for the mosaic theory, 

 it is particularly interesting to know that the egg of Triton, 

 which represents the other section (the urodela), falls in 

 with the sea-urchin, Amphioxv*, and hydroids, as concerns 

 the developmental ability of the separated cells of the two- 

 cell stage. For this information we are indebted first of all 

 to Ainedeo Herlit/ka. 



This power of developing whole animals from portions of 

 the egg has been proved to exist in several other groups, 

 but enough detail has now been adduced to show conclu- 

 sively that the mosaic conception of the organism contains 

 only a modicum of truth. The observations here briefly set 

 forth, with others of like import, led Wilson to declare: "In 

 its original form the mosaic theory has, I believe, received 

 its death-blow." "' 



Going still farther, Wilson said in the same discourse, 



I will here point out one all-important point which is, defi- 



itely established by the work of Driesch and other experi- 

 mentalists, and which is accepted by all opponents of the 

 mosaic theory, namely, that the cell cannot be regarded as 



n isolated and independent unit. The only real unity is 

 at of the entire organism, and as long as its cells remain 

 continuity thev are to be regarded, not as morphological 

 individuals, but as speciali/ed centres of action into which 

 the living body resolves itself, and bv means of which the 



hysiological division of labor is effected." 6 



It was these discoveries, antithetic to those which led to 

 the mosaic theory, that begot in Driesch's mind the concep- 

 tions of "totipotcnce," "prospective significance," and the 

 ''harmonic equipotential system." 



The formal definition of "totipotence," and of "prospec- 

 tive significance" mav be given here since thev concern pri- 

 marily the cells of the embryo. "Totipotence [is the pos- 

 session by] a part of the germ as yet not at all or but 

 slightly 'specified' of a form-producing power similar to that 



