At whatever period of life a new character first appears, it generally remains latent in the offspring until a corresponding age is attained, and then is developed. When this rule fails, the child generally exhibits the character at an earlier period than the parent. On this principle of inheritance at corresponding periods, we can understand how it is that most animals display from the germ to maturity such a marvellous succession of characters.
Finally, though much remains obscure with respect to Inheritance, we may look at the following laws as fairly well established. Firstly, a tendency in every character, new and old, to be transmitted by seminal and bud generation, though often counteracted by various known and unknown causes. Secondly, reversion or atavism, which depends on transmission and development being distinct powers: it acts in various degrees and manners through both seminal and bud generation. Thirdly, prepotency of transmission, which may be confined to one sex, or be common to both sexes. Fourthly, transmission, as limited by sex, generally to the same sex in which the inherited character first appeared; and this in many, probably most cases, depends on the new character having first appeared at a rather late period of life. Fifthly, inheritance at corresponding periods of life, with some tendency to the earlier development of the inherited character. In these laws of Inheritance, as displayed under domestication, we see an ample provision for the production, through variability and natural selection, of new specific forms.
REFERENCES
[1] See Youatt on Cattle, pp. 92, 69, 78, 88, 163; and Youatt on Sheep, p. 325. Also Dr. Lucas ‘L’Héréd. Nat.,’ tom. ii. p. 310.
[2] ‘Héréd. Nat.,’ tom. ii. pp. 112-120.
[3] Sir H. Holland, ‘Chapters on Mental Physiology,’ 1852, p. 234.
[4] ‘Gardener’s Chronicle,’ 1860, p. 270.
[5] Mr. N. H. Smith, ‘Observations on Breeding,’ quoted in ‘Encyclop. of Rural Sports,’ p. 278.
[6] Quoted by Bronn, ‘Geshichte der Natur,’ b. ii. s. 170. See Sturm, ‘Ueber Racen,’ 1825, s. 104-107. For the niata cattle, see my ‘Journal of Researches,’ 1845, p. 146.
[7] Lucas, ‘L’Hérédite Nat.,’ tom. ii. p. 112.