THE EVOLUTION OF LIVING BEINGS. 2J 



We thus get the following definitions: 

 Linneon: to replace the term species in the Linnean 

 sense, and to designate a group of individuals which 

 resemble one another more than they do any other indi- 

 viduals. 



To establish a Linneon consequently requires 

 careful morphological comparison only. 

 Jordanon : to replace the term species in the Jordanian 

 sense, viz: mikrospecies, elementary species etc. and 

 to designate a group of externally alike individuals 

 which all propagate their kind faithfully , under condi- 

 tions excluding contamination by crossing with indivi- 

 duals belonging to other groups, as far as these external 

 characters are concerned, with the only exception of 

 noninheritable modifications of these characters, cau- 

 sed by the influences of the surroundings in the widest 

 sense, to which these individuals or those composing 

 the progeny may be exposed. 



To establish a Jordanon, morphological compari- 

 son alone consequently does not suffise; the trans- 

 mittability of the characters by which the form was 

 distinguished, must be proved by experimental bree- 

 ding. 

 Species: to designate a group of individuals of identical 

 constitution, unable to form more than one kind of 

 gametes; all monogametic individuals of identical con- 

 stitution consequently belong to one species. 



To establish a species, neither morphological com- 

 parison alone, nor experimental breeding by itself is 

 sufficient, nor are the two combined ; hybrid analy- 

 sis is required in addition. 



