New Characters in Phlogeny 217 



for each variation of the germ substance to appear or 

 to become active, either from the beginning, or at any 

 time at all during the ontogeny? 



"The phenomena of latency" says Osborn, "speak 

 absolutely against Weismann's conception, according to 

 which phylogenetic development would take place in the 

 germ plasm by selection of advantageous elements, and 

 elimination of disadvantageous elements. These phe- 

 nomena of latency indicate that the phylogenetic process 

 does not consist in an elimination but in a shoving of 

 certain characters into the background (Zurickdrangung) 

 during the later stages of ontogeny." 



Osborn cites as example the well known experi- 

 ments of Cunningham on the color of the asymmetrical 

 flat fishes, pleuronectids, on whose lower colorless side 

 artificial illumination is followed by a reappearance of the 

 pigment disposed in the same designs and in the same 

 colors as on the upper side, and also Agassiz's experi- 

 ments according to which the young of these same fishes 

 retain their original symmetry when they are kept at the 

 surface of the water for a longer time than under normal 

 conditions. "According to these experiments," Osborn 

 says very rightly, "progressive inheritance (and so phylo- 

 geny) appears to represent rather a process of substitu- 

 tion or of addition than one of true elimination in Weis- 

 mann's sense." 165 Thus these facts also speak in favor 

 of the conception that phylogeny rests upon an addition 

 of new characters and their superimposition upon the old. 



We can see that to explain by the inheritance of ac- 

 quired characters this addition of a new character to the 



1 * 5 Osborn: Alte und neue Probleme der Phylogenese. Ergebn. 

 d. Anat. u Entwicklungsgesch., herausg. v. Merkel u. Bonnet. Bd. 

 III. 1893. Weisbaden, Bergmann, 1894. P. 610, 619. 



