As an attempt to explain gastrulation, the origin of the germinal layers and many other events of development, the doctrine of determinants has reversed cause and effect. Certain cells do not become invaginated into the segmentation cavity because they possess groups of determinants that impel them to the assumption of inner layer characters. The reverse is the truth. Local conditions of growth cause the invagination of a set of the cells of the blastosphere-wall. This invaginated layer of cells, brought into a new position with regard to its environment, becomes the endoderm and receives the stimulus to assume the character appropriate to the new environment. It is unlogical to speak of endoderm in the fashion of many textbooks and treatises on embryology, while the so-called endoderm cells still form part of the outer surface of the blastosphere, or even while they are still in process of formation by cleavage. For 'inner germinal layer' implies a condition of position which is created by the invagination. In fact, it is impossible, in thinking of the gastrula as in thinking of the blastosphere, to conceive that in the egg, which is a simple cell, there can be preformed by material particles in the nucleus a condition which implies the existence of two layers of cells. Thus analysis of a special case leads to the same conclusion as is reached by the general reasoning of the earlier part of this section. FOOTNOTES: [7] _The Germplasm_, pp. 68, 69. [8] The following treatises contain criticisms of Weismann's theories: W. Haacke, _Gestaltung und Vererbung_; Leipzig, 1893; Herbert Spencer, articles in _Contemporary Review_ (1893-94); Romanes, _An Examination of Weismannism_; Longmans, 1893.