BIOGENETIC LAW 79 



plasm tlie inheritance of the new generation is made up of the 

 id complex of the preceding one. A new determinant or group 

 of determinants can never come independently into existence, 

 but arises through a variation effected in the preceding group. 

 As spontaneous variations, however, never effect a change in 

 all the homologous determinants of the germ-plasm, but only 

 in a majority, a minority of the old determinants, representing 

 the former condition of the organ which has been readapted to 

 altered circumstances, stUl remains in the germ-plasm. This 

 nainority of old determinants may persist throughout long 

 periods, but slowly, though surely, its influence on the ontogeny 

 diminishes in the course of successive generations. For a time 

 the persistent determinants of a former organ may continue to 

 manifest themselves somatically throughout the whole course 

 of the Ufe-history as a rudimentary organ, as in the case of the 

 appendix vermiformis in the human species, which persists 

 during the whole hfe of the individual ; but with the progress of 

 time and the accumulation of new variations, implying con- 

 tinuous readaptation, the nutritive supply of such determinants 

 becomes ever less, the force of the determinants becomes ever 

 weaker in consequence, and the determinants can only manifest 

 themselves somatically during a longer or shorter period of the 

 embryogeny. The gill-clefts which served as respiratory organs 

 for our fish ancestors, and which still appear as vestigial struc- 

 tures in the human embryo, condemned to all but complete 

 disappearance before birth, are a case in point. 



To return, after this digression, to the LamarcMan theory, we 

 have observed that the degeneration of the wings — and, let it 

 be added, of the ovaries — in the worker ants shows that regres- 

 sive variation can set in where all possibility of hereditary trans- 



viated, recapitulation of the history of the species — and cenogenesis — i.e., 

 a modification of the historical sequence brought about by the more recent 

 adaptations of various stages in the ontogeny to new conditions. Both 

 palingenesis and cenogenesis find an explanation in the determinant theory. 



