56o 



THE PURE LINE HYPOTHESIS. 



It is inherently probable that some of the red offspring; were 

 of such a nature as to be unable to produce non-red offspring, 

 and such individuals, judging from other cases, would tend to 

 be of a more intense red than those which can produce both red 

 and non-red offspring. 



In order that the material should be as homogeneous as 

 possible for determining the hereditary transmission of the in- 

 tensity of colouration, we should only use parents and offspring 

 which are gametically similar. Owing to the nature of the 

 material, it is necessary to take the parents which are capable of 

 producing both red and non-red off'spring, and also the members 

 of the families that are able to do likewise. In the latter case 

 this may doubtless be roughly effected by removing from each 

 family one-third of the more intensely coloured individuals. 

 Although this procedure cannot be entirely reliable, yet its appli- 

 cation will give better results, since the material will be more 

 homogeneous than it otherwise is, and the only other course 

 would be to raise families from each of the 141 off'spring, and in 

 this way to determine their gametic nature. 



