Darwinism To-Day; A Discussion of Present-Day Scientific Criticism of the Darwinian Selection Theories, Together with a Brief Account of the Principal Other Proposed Auxiliary and Alternative Theories of Species-Forming

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER IV. DARWINISM ATTACKED (CONTINUED): THE THEORY OF NATURAL SELECTION (CONTINUED). Certain objections urged by various authors may be said to concern themselves more with the character of the varia- Objection based tions themselves and the possibilities of their on the linear and accumulation by selection, than with the manner quantitative and non-qnalitative of their occurrence. For example, de Vries ' afl.n" denies the species-forming capacity of Dar- winian selection of Darwinian (fluctuating) variation, on the ground that these variations are only "linear," and thus cannot afford a basis for the creation of new forms. Already existing bodies, organs, and parts can be enlarged or made smaller, made smoother or rougher, made bluer or less blue, greener or less green, that is developed plus-ward or minus-ward, but by this nothing really new is created. But, declares de Vries, the differentiation of organs consists, taken by and large, in the development of actually new characteristics; therefore in such material as that presented by the linear variations of Darwin, selection cannot have the necessary basis for this production of new characteristics. Gustav Wolff reiterates the same objection in his declaration that while the theory of natural selection may get on decently well when modifications embodying only quantitative changes in parts or organs are concerned, it is completely at a loss to account for modifications or adaptations requiring as basis qualitative changes. Even the warmestadvocates of the selection theory have to admit, says Wolff, that they face a serious matter here. Weismann ' is quoted as follows: "Wenn man sich die Umwandlung deshalb in grosseren Schritten und durch Variationen von qualitativer Natur geschehend denkt, so wird man iib...