This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1899 edition. Excerpt: ... APPENDIX G. TEE INHERITANCE OF FTNCTIOXALLT-CArSED MODIFICATIONS. In Part II, Chapter. XA, I have confessed that the process by which a structure changed by use or disuse affects the spermcells or germ-cells whence arise descendants, is unimaginable: without, however, inferring that therefore such a process does not exist. "With others it seems different. Some three years ago the following expression of opinion came to me from a zoological expert: -- "Many zoologists--most of us here at Cambridge--are intensely opposed to the doctrine of the inheritabilitv of acquired variations Even assuming that the developmental power of a germ is determined bv its molecular structure (and I for one would question this--Driesch and his school when they find that they can squeeze a developing egg into all sorts of shapes without altering the final result, that one blastomere in an egg which has divided into 8 is still able to reproduce a whole embryo--question it also we still fail to conceive any means by which, for instance, a change in the development of a muscle or nerve can effect a corresponding change in that part of the germ which is destined to produce a corresponding part in the descendant.' Here it will be observed that belief in the inheritance of structural effects wrought by use and disuse, is rejected because of inability "to conceive anv means" by .which the modifications produced in an organ can effect a correlated modification in the germ of a descendant: failure to conceive is the test. The implication is that some alternative hypothesis is accepted because the correlating of a variation in an organ with a corresponding germ-variation is effected by a means which it conceivable. This is the hypothesis of Weismann. Concerning its...