Heredity in the Light of Recent Research (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated.1912 Excerpt: ... CHAPTER IV THE STATISTICAL STUDY OP HEREDITY In studying heredity, either of two methods may be adopted. We may either choose a character and observe or measure its development in a large number of parents and in their children, and so deduce the average extent of resemblance between parents and children for that character; or we may consider a number of individual cases separately, and endeavour to discover the manner in which the character appears in the children who have parents or ancestors possessing it. With regard to the first method Prof. Pearson has written 'We must proceed from inheritance in the mass to inheritance in narrower and narrower classes, rather than attempt to build up general rules on the observation of individual instances.' And '...the very nature of the distribution...seems to indicate that we are dealing with that sphere of indefinitely numerous small causes, which in so many other instances has shown itself only amenable to the calculus of chance, and not to the analysis of the individual instance' 25, 'Math. Contrib. III.' Phil. Trans. Roy. Soc. A, 1896, p. 255, The second method on the other hand has been used in cases where the causes of variation appear to be few and definite, and seeks to isolate these causes. The first method is thus clearly adapted especially to characters which vary continuously and which can be measured; the second to characters which vary discontinuously and can be sharply separated into classes. The first method gives on the whole the average intensity of inheritance, but little information with regard to its probable development in individual cases; the second attempts to answer the question in what manner the character will be distributed among the offspring in any family. The founder of the modern s...