( Ixx ) 



pairing between a particular male and female. And Mr. 

 Prout informs me that this is sometimes, though not as a rule, 

 the case with the Geometric! stirps. 



All the results of the second and third generations seem 

 to be capable of Mendelian explanation if we call the melanic 

 strain the Dominant and the red forms Recessives. Fortius 

 purpose all the parents of the melanic broods of the second 

 generation must be assumed to be Dominant Recessives, while 

 the male parent of brood C 7 x C 7 (third generation— 

 (melanic male paired with a red female) must be assumed to 

 be a pure Dominant, as all the offspring were melanic. And 

 again both the parents of brood C 9 x C 7 (third generation) 

 must also have been Dominant Recessives. On the other 

 hand, at least one of the parents of the remaining melanic 

 broods of the third generation, broods C 9 x C 9 and 

 7x02, must have been for Mendelian purposes a pure 

 Dominant. 



The red parents throwing all red offspring will of course 

 be Recessives. So far all is straightforward, but if we 

 attempt to apply the principle backwards instead of forwards, 

 we come to a serious difficulty in respect to the first genera- 

 tion, as the results do not tally with either the supposition 

 that the male parent was "pure Dominant" or Dominant 

 Recessive. 



FIRST GENERATION 



ACTUAL RESULTS 



Brood B. 

 Remit 



Brood C. 

 Result. 



M<<!< parent dark slate (non-melanic) 

 /■ malt Red (non-melanic) 

 Most of the larvae were List owing to an 



accident but one slate-coloured speci- 

 men and one red one were hred. The 

 " lied" specimen of this brood was the 

 mali parent of Brood B x C. 

 Male Melanic. Female red. 

 21 Melanic ( = 40%) 32 Red ( = 80%) 



CORRECT MENDELIAX PROPORTIONS 



If male D. R. x female R. Result should be 

 50% Melanic, 50% Red. 



Or if male O. D. x female R. 

 100, Melanic. 



Result should be 



Brood C 2. 

 Result. 



Male Melanic. 

 Bacot 60 Melanic 

 i lardnei 21 Melanic 



Trout 17 Melanic 



SECOND GENERATION 



Female Melanic. 

 26 Red. 

 5 Red. 



S Red. 



Brood C. If both parents D. R. Result should be 

 75% Melanic, 25% Red. 



98 = ' 



38 = 27°: 



