542 



The Museum Gazette 



namely, the short-haired offspring of long-haired and short- 

 haired parents — it will be found (i) that if a number of short- 

 haired hybrids are bred with pure long-haired individuals the 

 litters will have on an average equal numbers of long-haired 

 and short-haired individuals ; (2) that if the short-haired 

 hybrids interbreed the offspring will consist of three quarters 

 short-haired and one quarter long-haired individuals ; and 

 (3) that if the short-haired hybrids are mated with pure short- 

 haired individuals all the offspring will be short-haired. 



Mendel explained these results by his theory of the purity 

 of the germ cells. He maintained that the hybrids give off two 

 kinds of germ-cells (gametes), one kind bearing the character 

 of one parent and the other kind bearing the character of 

 the second parent ; that the two kinds are given off in equal 

 numbers ; and that no germ cells are produced bearing both 

 characters. 



Putting L for a long-haired gamete and S for a short-haired 

 gamete the results may be illustrated thus : — 



Case 1. 



Pure long-haired rabbits produce gametes ... LL 

 Hybrid short-haired rabbits produce gametes L S 

 Hence the possible combinations are L L, L S, L L, L S ; 



in other words, long-haired and short-haired offspring are 



produced in equal numbers. 



Case 2. 



Hybrid short-haired rabbits produce gametes... L S 

 ,, ,, ,, ,, L S 



The possible combinations are L L, L S, L S, S S, and 

 since L is a recessive character we get three short-haired to 

 one long-haired offspring. 



Case 3. 



Pure short-haired rabbits produce gametes ... S S 

 Hybrid „ „ „ „, ... L S 



The combinations are S L, S S, S L, S S, and as L is a 

 recessive character, all the offspring have short hair. 



