Embryos and Ancestors

Abstract

IN 1930 Dr. de Beer published a small and stimulating book under the title “Embryology and Evolution”. In it he attempted to reorientate general views relating to ‘recapitulation’ in evolution. Beginning with a statement of Von Baer's laws, he described their modification at the hands of Haeckel, who in his biogenetic law abandoned Von Baer's principles of progressive deviation and instead implied, as Dr. de Beer puts it, that phylogeny is due to the “successive tacking on of new final stages to the existing adult stages of animals”. Haeckel's biogenetic law had, of course, come under considerable fire before Dr. de Beer attempted to redefine the problem. Its main shortcoming was the fact that the order in which characters appear in phylogeny is frequently completely different from that in which they appear in ontogeny. The term heterochrony is applied to this alteration in the sequence of stages.

Embryos and Ancestors

By Dr. G. R. de Beer. (Monographs on Animal Biology.) Pp. x + 108 + 2 plates. (Oxford: Clarendon Press; London: Oxford University Press, 1940.) 7s. 6d. net.