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 Qgg of Triton, 

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

 with the sea-urchin, Amphioxus, and hydroids, as concerns 

 the developmental abiHty of tlie separated cells of the two- 

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

 to Amedeo Herlitzka. 



This power of devclo])ing whole animals from portions of 

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

 but enougli 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 deatli-blow." "• 



Going still farther, Wilson said in the same discourse, 

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

 nitely 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 

 an isolated and independent unit. The only real unity is 

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

 in continuity they are to be regarded, not as morphological 

 individuals, but as specialized centres of action into which 

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

 physiological division of labor is effected." *^ 



It was these discoveries, antithetic to those which led to 

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

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

 "harmonic equipotential system." 



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

 tive significance" may be given here since they 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 



