SHORTER ARTICLES AND DISCUSSION 



COLLINS 'S REMARKS ON THE VIGOR OF FIRST 

 GENERATION HYBRIDS 



In a review of the theories regarding hybrid vigor Collins^ 

 has attempted to show that, the two objections wliieh were long 

 upheld as preelndin- the possibility of dominance acconnting 

 for heterosis were without foundation. The supin-ession of dele- 

 terious factors, he eoiisidfrs. is a(hM|ii,i1i' to account for the ob- 

 served facts without rousKlci'iii- ilir phrnoiiiriioii (if linkage. 



The two objections wiiidi wrrc raised against the hypothesis 

 of dominance as a factor in hybrid vigor befoi'c the importance 

 of linkage became generally known are as follows: (1) Domi- 

 nance of independent factors would give an asymmetrical distri- 

 bution to the progeny populations of those individuals which 



of II, c n(,rinal ru'rv... lie puini. nut tliat. ui'tli characters \L 

 ].cndciii uiuwi a lar-.c nniiilicr nt' fa. Mors. ,„,!> populations with 



exhibit any nuticoablr tendency toward .kewne... This is a 



numbers nearly equals the comi)ine(l ranne of rl I'iirinal races 



as exhibited by the characters which show heterosis the niunber 

 of main factors which govern the exiiression ,,t' this particular 

 character can not be large. Therefore, it n were merely a mat- 



