Chap. I. UNDER DOMESTICATION. 27 



even the dahlia, etc. ; and it is really surprising to note the 

 endless points in structure and constitution in which the varie- 

 ties and sub-varieties differ slig'litly from each other. The 

 whole organization seems to have become plastic, and tends to 

 depart in a slight degree from that of the parental type. 



Any variation which is not inherited is unimportant for us. 

 But the number and diversity of inheritable deviations of struc- 

 ture, both those of slight and those of considerable physiological 

 importance, are endless. Dr. Prosper Lucas's treatise, in two 

 large volumes, is the fullest and the best on this subject. No 

 breeder doubts how strong is the tendency to inheritance : that 

 like produces like is his fundamental belief : doubts have been 

 tlirown on this principle only by theoretical writers. When 

 any deviation of structure often appears, and we see it in the 

 father and child, we cannot tell Avhether it may not be due to 

 the same cause having acted on both ; but when among indir 

 viduals, apparently exposed to the same conditions, any very 

 rare deviation, due to some extraordinary combination of cir- 

 cumstances, appears in the parent — say, once among several 

 million individuals — and it reappears in the child, the mere 

 doctrine of chances almost compels us to attribute its re- 

 appearance to inheritance. Every one must have heard of 

 cases of albinism, prickly sldn, hairy bodies, etc., appearing in 

 several members of the same family. If strange and rare devia- 

 tions of structure are really inherited, less strange and com- 

 moner deviations may be freely admitted to be inheritable. 

 Perhaps the correct way of viemng the whole subject, Avould 

 be, to look at the inheritance of every character whatever as 

 tlie rule, and non-inheritance as the anomaly. 



The hiAvs governing inheritance are for tlie most part un- 

 Icnown. No one can say why the same peculiarity in tlifferent 

 individuals of the same species, or in different species, is some- 

 tiiucs inherited and sometimes not so; why the child often re- 

 verts in certain characters to its grandfather or grandmother or 

 more remote ancestor ; why a peculiarity is often transmitted 

 fi'om one sex to both sexes, or to one sex alone, more commonly 

 but not exclusively to the like sex. It is a fact of some impor- 

 tance to us, that jK'culiarities appearing in the males of our 

 domestic breeds are ofLen transmitted, either exclusively or in 

 a nmch greater degree, to tlie males alone. A much more im- 

 portant rule, which I think may be trusted, is that, at Avhatevrr 

 period of life a peculiarity first appears, it tends to reappear in 

 the ollspring at a corresponding age, though sometimes earlier. 



