Boveri also tried fertilizing a non-nucleated piece of the egg of one species of sea-urchin with a spermatozoon of another species. He found that the embryo that develops is of the type of the species from which the spermatozoon has come, and he concluded that the nucleus determines the character of the larva, and that the protoplasm has no influence on the form. The evidence from which Boveri drew his conclusion is not beyond question. It has been shown by Seeliger (’95) and myself (’95) that if whole eggs of the species _Sphærechinus granularis_, used by Boveri, are fertilized by the spermatozoa of the other species, _Echinus microtuberculatus_, there is great variability in the form of the resulting larvæ. Most of them are intermediate in character between the types of larvæ of the two species, but a few of them are like the paternal type. Vernon (’99) has more recently shown that the character of hybrids is dependent upon the ripeness of the sexual products of the two parents. If, for instance, the eggs (sphærechinus) are at the minimum of maturity, the hybrids are more like the male (strongylocentrotus). It remains, therefore, still to be shown whether or not the protoplasm has any influence on the form of larva that comes from a non-nucleated piece, fertilized by a spermatozoon of another species. That the nucleus of the male does have an influence on the form of the animal is abundantly shown by the inheritance of the peculiarities of the father through the chromatin of the spermatozoon. _THE CLOSING IN OF CUT-EDGES_