IN THE TROPICS. 
313 
(We have here, be it noted, two entirely new combinations 
of characters, viz., Ab and aB, not seen in the parent forms). 
On examining a further generation F 3 the offspring of the 
9 AB plants of F 2 are found on the average to be as follows :— 
The offspring of 4 plants include 9AB, 3Ab, 3aB, lab. 
„ 2 „ 3AB, I Ab. 
„ 2 „ 3 AB, laB. 
,, 1 „ AB exclusively. 
The 3Ab plants (F 2 ) produce the following offspring :— 
The offspring of 2 such plants include 3Ab and lab. 
„ 1 „ Ab only. 
The 3aB plants produce the following offspring :— 
The offspring of 2 plants include 3aB, and lab. 
„ 1 „ aB only. 
And, finally, the ab plants produce nothing but ab. 
The sixteen plants of F 2 are thus shown by their offspring 
to be of the following kinds :— 
One each of the pure forms : AB, Ab, aB, and ab, which 
breed true. 
Four heterozygotes in respect of both pairs of characters ; 
these give in F 3 the same series as the original heterozygotes 
of F! (AaBb) gave in F 2 ; they are, therefore, of the same 
form—4 AaBb. 
Also the following four sets of two plants each : — 
2AB giving AB and Ab ; these we may write 2ABb. 
2AB 
,, AB „ aB ; 
>> 
5? 
„ 2AaB. 
2Ab 
„ Ab „ ab ; 
„ 2Aab. 
2aB 
„ aB „ ab ; 
5? 
„ 2aBb. 
Altogether, therefore, AB + Ab + aB + ab + 2ABb + 2aBb4- 
2AaB + 2Aab + 4AaBb, which is the result of combining the 
formulae — (A + 2Aa + a), (B + 2Bb + b) each of them 
characteristic of F 2 of a monohybrid. The relation of the 
