258 ERNST HAECKEL AND CARL GEGENBAUR 



paper on the Gastr.ta theory (I875), 1 he had to worR out 

 a distinction between palingenetic and cenogenetic characters, 

 of which much use was made by subsequent writers. 



The distinction may be given in Haeckel's own words: 

 "Those ontogenetic processes," he writes, "which are to be 

 referred immediately, in accordance with the biogenetic law, 

 to an earlier completely developed independent ancestral fo)-in, 

 and are transmitted from this by Jiercdity, obviously possess 

 primary importance for the understanding of the casual- 

 physiological relations ; on the other hand, those develop- 

 mental processes which appear subsequently through 

 adaptation to the needs of embryonic or larval life, and 

 accordingly can not be regarded as repeating the organi- 

 sation of an earlier independent ancestral form, can clearly 

 have for the understanding of the ancestral history only 

 a quite subordinate and secondary importance. 



" The first I have named palingenetic, the second ceno- 

 genetic. Considered from this critical standpoint, the \vhole 

 of ontogeny falls into two main parts: First, palingenesis, or 

 'epitomised history' {Auszugsgeschichte}^ and second, ceno- 

 gencsis, or ' counterfeit history ' (Falschungsgeschichte). The 

 first is the true ontogenetic epitome or short recapitulation 

 of past evolutionary history ; the second is the exact 

 contrary, a new foreign ingredient, a falsifying or concealing 

 of the epitome of phylogeny." 



As examples of palingenetic processes in the development 

 of Amniotes, for instance, may be quoted the separation of 

 two primary germ-layers, the formation of a simple noto- 

 chord between medullary tube and alimentary canal, the 

 appearance of a simple cartilaginous cranium, of the gill- 

 arches and their vessels, of the primitive kidneys, the 

 primitive tubular heart, the paired aorta; and the cardinal 

 veins, the hermaphroditic rudiment of the gonads, and so on. 

 Cenogenetic processes, on the other hand, include such 

 phenomena as the formation of yolk and the embryonic 

 membranes, the temporary allantoic circulation, the navel, 

 the curved and contracted shape of the embryo, and the like. 



The most important phenomena to be included under 



1 Jenai\chc /.citschrift, ix., pp. 402-508, 1875. 



2 Loc. cit.. ix., p. 409. 



