THE BOOK OF POULTRY. 



some the factor for single comb only. In no 

 gamete will the character for both rose and 

 single comb be found. This explains why two 

 birds both impure rose-combs will breed pure 

 rose-comb and pure single combs. 



To the Mendelist a bird is composed of a 

 great number of allelomorphs, and so far the 

 action of a few only are known. The practical 

 use of Mendelism to the fancier is confined to 

 those allelomorphic characters which have been 

 completely investigated. Many experimenters 

 are at work, and as time goes on the in.vestigation 

 of more and more of these allelomorphic char- 

 acters will be completed. 



Gregor Johann Mendel was born on July 22nd, 

 1822, at Heinzendorf bei Odrau, in 

 Mendel Austrian Silesia. He was given a good 

 education in his youth and entered the 

 monastery of Briinn in 1843. He was ordained 

 priest in 184". From 1851 to 1853 he studied 

 at Vienna, and in the latter year he returned to 

 Briinn and took up teaching in the Realschulc 

 there. He relinquished this work in 1868 on 

 his appointment as abbot. His classic experi- 

 ments on the edible pea {Pistaii sativum) were 

 carried out in the cloister garden, and the re- 

 sults were published in the Proceedings of the 

 Natural History Society of Briinn under the title 

 of " Experiments in Plant Hybridisation." He 

 died January 6th, 1884. It does not appear that 

 his work was known to na'turalists, though he 

 at one time explained it to the botanist Carl 

 Niigeli, and it was not until the rediscovery of 

 his paper in 1900 that the real value of his con- 

 tributions published in 1865 was understood. 

 The rewards of scientific workers are not always 

 commensurate with their labours ; some receive 

 immediate recognition, whilst others, like Mendel, 

 have to wait some decades before the true value 

 of their work is known. Let us hope that the 

 pursuit of knowledge is in itself a sufficient 

 reward to them for their efforts. 



Mendel's experiments show him to have been 

 a remarkable genius. This is proved by the 

 discrimination he displayed in selecting the 

 right material to work with and the right char- 

 acters to observe ; by the absolute accuracy of 

 his results (as borne out by others who have 

 lately repeated his experiments) ; by the min- 

 ute and clear record he kept ; and, above all, 

 by his insight into the true meaning of the 

 facts he observed. 



He crossed two peas which difl'ered in height, 



one being about 6ft. and the other about ift. 



The seeds produced by this cross- 



His fertilisation were sown and ail grew 



Experiments i„to tall plants. This tall generation 



from the cross-bred seeds is called 



F, (first filial generation). As all these plants 

 were tall, Mendel called the character which 

 prevailed the domuiaiit character, and the char- 

 acter which was unable to appear the recessive. 



P"i generation was self-fertilised and its 

 seeds sown ; the plants this time grew up, 

 not all tall as F^, but tall and dwarf in the 

 proportion of 3 to I. This generation is called 

 Y .^ (second filial generation). On being self- 

 fertilised, the plants of F^, were seen to be of 

 three kinds : — 



{a) Pure Dominants. Tall plants which gave 

 tails only for the next and succeeding genera- 

 tions. 



{b) Impure Dominants. Tall plants which 

 gave tails and dwarfs in the same proportion 

 as F,. 



(f) Pure Recessives. Dwarf plants which 

 gave dwarfs only in the next and succeeding 

 generations. 



On testing the tails of F., generation it was 

 found that the proportion of the pure tails (a) 

 to impure tails {U) was i to 2. Thus pure 

 talis and pure recessives were equal in pro- 

 portion and together formed half the pro- 

 duce. 



Expressed as under, the result can be clearly 

 understood : — 



25'';o 50^.0 _ 25% 



Pure Dominant Impure Dominant Recessive 



Tallness and dwarfness are allelomorphs, 

 unit characters, transmitted as a whole from 

 parent to progeny. Thus regarding them, it 

 is easy to explain the above results. Fj gene- 

 ration was produced by the union of male and 

 female gametes, each one bearing either the 

 dominant or the recessive character, and so the 

 zygote formed by their union was impure 

 in that it contained both elements. When F, 

 came to form gametes, then segregation occurred. 

 The characters (united in the zygote) separated 

 or segregated and each gamete carried one, 

 only one, and one as a whole of the characters, 

 cither the dominant (tall) or the recessive 

 (dwarf). When fertilisation took place a 

 gamete carrying the dominant character could 

 unite with one also carrying the dominant 

 character and so form a pure dominant, DD, 

 or it could unite with one carrying a recessive 

 character and so form an impure dominant 

 (DR). Likewise a gamete carrying a recessive 

 character could unite with one carrying a domi- 

 nant character and so form an impure dominant 

 (DR), or with one carrying a recessive char- 

 acter and so form a pure recessive (RR). 

 This exhausts all possible combinations 



