COAT CHARACTERS IN GUINEA-PIGS AND RABBITS. 



Darbi shire ( : 04) , Castle & Allen ( : 03), Bateson ( : 03) , Allen ( : 04) , 

 and others. The evidence that segregation of the dominant and 

 recessive characters occurs when the cross-bred pigmented animals 

 form gametes is not less clear. The matter can be conveniently tested in 

 two ways : (i) By mating a cross-bred with an albino animal, when 

 half the young should be pigmented, the other half albino, if segre- 

 gation occurs as demanded by Mendel's law ; (2) by mating hybrids 

 inter se, when we should expect three-fourths of the young to be 

 pigmented, one-fourth albino. The first sort of mating has in these 

 experiments produced 211 pigmented and 214 albino young, where 

 the expectation is 212.5 f eacn sort, which certainly is a very close 

 approximation. The second sort of mating has produced 264 pig- 

 mented and 112 albino young, the expectation being 282 pigmented and 

 94 albino young, i. e., there are 18 more than the expected number of 

 albinos in a total of 376 young, a fairly close approximation, but not 

 so close as that observed in the first case. 



Combining the results of all matings which are expected to produce 

 albinos, we get the following : 



This shows an excess over expectation of 19.5 albinos in a total of 

 801 young, or about 2.5 per cent. 



$7.1 C (.P) 



7.3 a 



$7.3* 



?207(?) 



FIG. 9. A genealogical table showing the character, as regards recessive albinism, of the young pro- 

 duced by three matings between a pure pigmented (f) and a hybrid pigmented animal. 



Matings of hybrid pigmented with pure pigmented animals have, as 

 expected, produced only pigmented offspring, which number 35 1 . The 

 Mendelian expectation is that half the young so produced will be pure 

 in character, half hybrid. Since the two sorts look alike, only indi- 

 vidual breeding tests will suffice to distinguish them. In certain cases 

 such tests have been made, the results showing that the expectation 

 based on theory is realized. 



Fig.9 shows the results of three different matingsof this sort in a single 



