Further Examination of the Cell-Theory 205 



anura), served as tlie starting point for the mosaic tlieory, 

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

 which represents the otlier section (the urodcla), falls in 

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

 the developmental ahility of the separated cells of the two- 

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

 to Amedeo Herlitzka. 



This power of developing whole animals from portions of 

 the Q^rg has been proved to exist in several other groui)s, 

 but enough detail has now been adduced to show conclu- 

 sively that the mosaic conce})tion 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- 

 nitely established by the work of Driesch and other exj^ri- 

 mentallsts, 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 

 ])hysiologIcal 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," "j)ros])ective 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 ]i()s- 

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

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



