E.S. Russell quotes:

From the point of view of the pure morphologist the recapitulation theory is an instrument of research enabling him to reconstruct probable lines of descent; from the standpoint of the student of development and heredity the fact of recapitulation is a difficult problem whose solution would perhaps give the key to a true understanding of the real nature of heredity.

The living thing is not the clay molded by the potter, nor the harp played upon by the musician. It is the clay modeling itself.