THE BOOK OF POULTRY. 



operations when the parental faults appear in 

 them. It enables the breeder to appraise the 

 breeding value of a bird in a more intelligent 

 way than he ever did before. It furnishes 

 an intelligent explanation of many empirical 

 methods which have been followed and enables 

 breeders considerably to extend these methods. 

 In breeding rose-comb birds, specimens very often 

 appear that are first class in all respects except 

 the comb, which is single. So far breeders have 

 not hesitated to use such birds for breeding. 

 IVIendelism explains such an appearance and 

 also shows us how pure rose-comb birds can be 

 bred from such a one. This will appear later 

 on when rose and single combs have been dealt 

 with as Mendelian characters. 



Mendelism suggests that cvciy breeder should 

 ':est and analyse the birds from which he breeds. 

 The birds are, in fact, to the breeder what the 

 test-tubes are to the chemist. By applying the 

 principles of Mendelism to his stock 

 Test the breeder will have a knowledge of 



his birds that he never dreamt of be- 

 fore. He will be able to know their strong points 

 and their weak points as breeders. Crossing 

 during the off season or in their first year will 

 quickly enable him to detect the weakness and 

 the strength of his birds. With this knowledge 

 he will know how to perfect their strong points 

 and how to guard against the weak. 



Most breeders have found that a certain two 

 birds do not mate well together. Mendelism 

 suggests that both should be analysed and the 

 reasons for this failure di'^covered. Having 

 done this, the breeder will be able, from a 

 similar knowledge of his other birds, to know 

 the right birds to mate together. In this way 

 pedigree will be a real and valuable asset to 

 every breeder. 



In the lowest organisms the race is propagated 

 by the organism growing and dividing into two 

 exactly similar parts, each part being 

 Life an exact reproduction of the parent ; 



Cycle after division it is impossible to say 



which is the parent and which is the 

 offspring. This mode of reproduction is confined 

 to organisms made up of one cell. As we ascend 

 in the scale of life, organisms are no longer 

 made up of one cell, but of many, and these 

 cells are differentiated in functions. Some are 

 set apart to form bone and organs of locomotion, 

 others form organs of digestion, and others 

 organs of reproduction, etc. In the unicellular 

 organism all these functions, locomotion, 

 digestion, reproduction, etc., are carried out in 

 the one cell. But no matter how complex the 

 animal may be in its initial stage, every organ- 

 ism springs from one cell, which is called the 



zygote. This z\-gote has been formed by the 

 union of two germ cells (gametes) derived from 

 a male and a female parent. The male germ 

 cell (gamete) is called spermatozoon ; the female 

 germ cell (gamete) is called the ovum. To 

 repeat, the zygote is the single cell which will 

 by repeated divisions form the new individual, 

 and it itself has been formed by the fusion, or 

 blending, into one cell of the male and female 

 gametes. This individual in time reaches the 

 adult stage and itself forms gametes, and so is 

 equal to taking its part in the reproduction of 

 its own species, and thus the life cycle is com- 

 plete from gamete to gamete. In the case of 

 the fowl the union between the male and female 

 gametes takes place in the upper portion of 

 tlie oviduct. The zygote so formed is con- 

 tained in the fertile egg and by incubation gives 

 rise to the chick which grows into the adult 

 fowl. 



Heredity has been defined as the tendency 

 which all living beings exhibit to assume the 

 structures and to perform the func- 

 What is tions characteristic of the species to 



Heredity? which the individual belongs, and to 

 transmit the same to their offspring. 

 We have just briefly touched upon the process by 

 which this transmission is brought about, and 

 from a consideration of it, it is clear that what- 

 ever the new organism receives from each parent 

 must be received through the gametes. The 

 problem of heredity resolves itself into the eluci- 

 dation of the laws which govern the transmission 

 of the parental characteristics to the offspring, 

 through the medium of the gametes. At the 

 outset a natural question arises as to whether 

 this process occurs in a definite and regular 

 way or in an indefinite and irregular way. If 

 the transmission of characteristics occurs in an 

 irregular way it follows that we can never hope 

 to gain a full insight into the scheme as a whole, 

 but can only follow it in the particular cases 

 we may examine. The examination of such 

 particular cases will not help the breeder much 

 if the results vary with each individual mating, 

 if not with each individual impregnation. Un- 

 less there is a regularity about the process which 

 extends to all cases, unless it follows definite 

 lines, the study of heredity, interesting as it 

 may be in particular cases, will not be of much 

 use to the breeder generally, and he will still 

 have to continue on empirical lines (which have 

 certainly produced excellent results in the past) 

 and he will leave severely alone a study which 

 cannot practically assist him. 



Mendelism points to the fact that the trans- 

 mission of parental qualities is effected in a 

 definite and regular way, and that being so it 



