ABSTRACT
All the phenomena of the embryonicor individual development may in reality fall into two different groups. The first group comprises the primaeval development or the recapitulative development, and exhibits all those primaeval conditions. The second group contains the disturbed or falsified development, and obscures the original figure of the individual development by the introduction of new and foreign shapes, and was acquired by the embryo only by adaptation to the peculiar conditions of the individual development. Man is at the beginning of his individual existence a simple egg, a single little cell, just the same as every animal organism which originates by sexual generation. The eggs of many lower animals differ from this in being naked cells, as the outer covering is wanting. The two series of organic development, the ontogenesis of the individual and the phylogenesis of the tribe to which it belongs, stand in the closest causal connection with each other.
