401 D. J. SCOURFIELD ON MENDELISM AND MICROSCOPY. 



and Saunders, on pea,*, stocks, and other plants ; Spillman, on 

 wheat ; Biffen, on wheat and barley ; Hurst, on orchids, peas, etc. 

 Experimental breeding of animals on Mendelian lines has been 

 carried out by Cuenot, on mice ; Bateson and Punnett, on poultry ; 

 ( lastle and Allen, on guinea-pigs, mice, and rabbits ; Darbishire, 

 on mice ; Hurst, on poultry and rabbits. 



All these workers and many others have obtained results for 

 certain characters which are obviously in accordance with Mendel's 

 law. Many beautiful examples of Mendelian inheritance in its most 

 typical form — i.e. accompanied by the phenomenon of dominance — 

 have been brought to light ; e.g. in maize, where seeds in the 

 ratio of three dominant to one recessive may be obtained for two 

 pairs of characters on the same cob.* But even when dominance 

 does not occur, and the hybrids, by the interaction of the charac- 

 ters of each pair upon one another, possess a special appearance 

 of their own, it has been shown that the inheritance of the 

 characters often strictly conforms to Mendel's law. In such 

 cases the 1:2:1 ratio is, of course, at once apparent in the 

 progeny of the hybrids — e.g. " Giant Lavender " among Chinese 

 primroses, " Blue Andalusians " among fowls, etc. Further, it 

 has been found that characters of the most subtle kind, such as 

 power of resisting disease, little peculiarities of habit, etc., may 

 be transmitted in accordance with the same law, and it now 

 appears reasonable to believe that characters of every conceivable 

 kind may come under its sway, presuming that the characters 

 are based upon differences in the germ-plasm, and not merely 

 produced by the action of the environment upon the individual. 



But more significant than the demonstration of the wide range 

 of characters obviously obeying Mendel's law have been the 

 extensions of the application of that law in explaining certain 

 apparently anomalous results. One of the most important 

 developments in this direction is due to Cuenot. 



In experimenting with mice, he, and others also, had been 

 puzzled by the unforeseen appearance of entirely new characters, 

 supeiimposed, so to speak, on a purely Mendelian inheritance of 

 certain other characters. For instance, hybrids between pure 

 races of grey and albino mice, although producing progeny in the 



Examples of maize-cobs showing the Mendelian ratios, grown by Mr. 

 R. II. Lock at the Royal Botanic Gardens, Peradeniya, Ceylon, are ex- 

 hibited in the Natural History Museum, South Kensington. 



