Page:Philosophical Review Volume 3.djvu/254

238 descent, heredity the science of descent. Weismann's theory of non-transmissibility is stated in contrast to the opposite theory of all the Neo-Lamarckians. A quality, to be transmitted, must be inherent in the type. The onus probandi rests with Spencer et al., and, as yet, they have not scientifically shown transmission to be a fact. The germ-plasm theory is threefold. There is the "id," composed of myriads of determinants, each of which is made up of a group of biophors, but forms a higher vital unit. The variety, possible for the determinant to give the biophors, is subject to environment only by inherent blastogenetic character. Reversion may thus be explained. The germ-plasm continuity theory confirms that of non-transmission. How, then, do species originate? If these two theories be accepted, natural selection and special creation coalesce; and evolution describes the process, not the power, of the origin. Another outcome of Weismann's theories is to take away the necessity of an indefinitely lengthened world chronology.

The theory of biophors and determinants does not carry us much beyond our notion of potentiality. It is a mere suggestion to say that the transmitted potentiality is due to transmitted biophors and determinants, and the statement fails practically to give a detailed explanation of the mysteries of organic development. Dr. Weismann attributes effective variation to "the constant recurrence of slight inequalities of nutrition in the germ-plasm," but he has not pretended to say how changes of nutrition produce the particular variations in the determinants of the germ-plasm. The salient features of Weismann's views are these, (1) The development of the individual from a fertilized ovum is essentially germinal. This is an unsound proposition. (2) Heredity is provided for by the constant holding in reserve of some of the germinal matter which increases by growth and cell division. This proposition, if taken broadly as a statement of the view that certain cells remain comparatively undifferentiated and retain the potentiality of reproduction, may be accepted. (3) Effective variation is provided for by the influence of "nutrition" upon the determinants contained in this reserve germ-plasm. This proposition seems to throw too much stress on the nutrition and environment, too little on the inherent activities of living matter.