ABORTIVE ORGANS. 59 



tiation which causes the resemblance of the higher in- 

 compkte, to the lower complete forms. To limit our- 

 selves to one example: it is quite incomprehensible 

 why the ear-bones of the mammal should be developed, 

 by the circuitous process of the formation of germinal 

 fissures, if it were a mere question of histological and 

 morphological differentiation. This explanation fails 

 also with regard to the whole class of the phenomena 

 of purposeless and abortive organs, and, finally, the 

 "evoluttcnary type" itself as it rules the groups and 

 regulates individual development, still remains without 

 an explanation. 



