16 



1. AB,ABb,AaB,AaBb. 



2. AaBb,Aab,aBb,ab. 



3. AB,ABb,AaB,AaBb. 



4. AaBb,Aab,aBb,ab. 



If, furthermore, the several forms of 

 the egg and pollen cells of the hybrids 

 were produced on an average in equal 

 numbers, then in each experiment the 

 said four combinations should stand in 

 the same ratio to each other. A perfect 

 agreement in the numerical relations 

 was, however, not to be expected, since 

 in each fertilisation, even in normal 

 cases, some egg cells remain unde- 

 veloped or subsequently die, and many 

 even of the well-formed seeds fail to 

 germinate when sown. The above as- 

 sumption is also limited in so far that, 

 while it demands the formation of an 

 equal number of the various sorts of 

 egg and pollen cells, it does not require 

 that this should apply to each separate 

 hybrid with mathematical exactness. 



The first and second experiments 

 had primarily the object of proving 

 the composition of the hybrid egg 

 cells, while the third and fourth ex- 

 periments were to decide that of the 

 pollen cells.^* As is shown by the above 

 demonstration the first and third ex- 

 periments and the second and fourth 

 experiments should produce precisely 

 the same combinations, and even in the 

 second year the result should be par- 

 tially visible in the form and colour 

 of the artificially fertilised seed. In the 

 first and third experiments the domi- 

 nant characters of form and colour, A 

 and B, appear in each union, and are 

 also partly constant and partly in hy- 

 brid union with the recessive char- 

 acters a and b, for which reason they 

 must impress their peculiarity upon 

 the whole of the seeds. All seeds should 

 therefore appear round and yellow, if 



18 [To prove, namely, that both were 

 similarly differentiated, and not one or other 

 only.] 



MENDEL 



the theory be justified. In the second 

 and fourth experiments, on the other 

 hand, one union is hybrid in form and 

 in colour, and consequently the seeds 

 are round and yellow; another is hy- 

 brid in form, but constant in the reces- 

 sive character of colour, whence the 

 seeds are round and green; the third is 

 constant in the recessive character of 

 form but hybrid in colour, conse- 

 quently the seeds are wrinkled and 

 yellow; the fourth is constant in both 

 recessive characters, so that the seeds 

 are wrinkled and green. In both these 

 experiments there were consequently 

 four sorts of seed to be expected— viz. 

 round and yellow, round and green, 

 wrinkled and yellow, wrinkled and 

 green. 



The crop fulfilled these expectations 

 perfectly. There were obtained in the 



1st Experiment, 98 exclusively round 

 yellow seeds; 



3rd Experiment, 94 exclusively 

 round yellow seeds. 



In the 2d Experiment, 31 round and 

 yellow, 26 round and green, 27 wrin- 

 kled and yellow, 26 wrinkled and 

 green seeds. 



In the 4th Experiment, 24 round and 

 yellow, 25 round and green, 22 wrin- 

 kled and yellow, 26 wrinkled and 

 green seeds. 



There could scarcely be now any 

 doubt of the success of the experiment; 

 the next generation must afford the 

 final proof. From the seed sown there 

 resulted for the first experiment 90 

 plants, and for the third 87 plants 

 which fruited: these yielded for the 



1st Exp. 3rd Exp. 

 20 25 round yellow seeds . AB 



23 19 round yellow and 



green seeds ABb 



IS 22 round and wrinkled 



yellow seeds AaB 



22 21 round and wrinkled 



green and yellow 



seeds AaBb 



