COAT CHARACTERS IN GUINEA-PIGS AND RABBITS. 



Darbishire ( : 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 each 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, /. c. , 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 

 Soi young, or about 2.5 per cent. 



$ 7. 1 a $7. 



7. 1 c (/>) 



7. 1 



7.3 



$7.3' 



$124 



'126' 



208 (P) $207(?) 2208(P 



O 32G (JP) 



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

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



Matings of hybrid pigmented with pure pigmented animals have, as 

 expected, produced only pigmented offspring, which number 351 . 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 matings of this sort in a single 



