540 



THE AMERICAN NATURALIST 



[Vol. LIII 



As tlie result of his investigations regarding sterility 

 to pollen, Darwin was able to render at least one service, 

 that of removing the obsession which had so long af- 

 flicted the study of the hybrid question, viz., the variety- 

 species discussion. He says : 



It can thus be shown that neither sterility nor fertility affords any 

 (la, 2:4). 



The question of the chemical and cvtological basis for 

 sterility or non-receptivitv to pollen, remains still in part 

 an open field for tlic invcstiii'ator. 



One of the iiio-t itii] loilMiit <niestions from our present- 

 day |)oiiit ot \ winch Dniwm investigated was the 

 relative vigor ot tirst-ut'iici-alion hybrids as compared 

 with tliat of their i)aivnts. The following allusions occur 

 in the "Origin of Species." 



Darwin comments on the fact that crosses between in- 

 dividuals of the same species, where thev differ to a cer- 

 tain extent, give increased \ mor and tcrtihty, while close 

 Icrtilization, long continucfh ahiio-i aiwavs leads to phvs- 

 ical de^-eneracv, and remark-: 



L.tu-.m tlu. ,lis!in.-i in.livi.lnals of the 

 i.-n,i<-t vm-i,>ii<.>. ii.rrcas... the number of the 



Darwin thoroughly investigated, as is well known, the 

 comparative relation of tlie offsprino- of crossed to those 



