Craniosynostosis and the pathological complex with which it is associated in the rabbit are not identical with the abnormalities seen in man; but apparently the two sets of conditions have enough in common to warrant the conclusion that they probably have a common mode of origin. The evidence so far obtained shows that in the rabbit these conditions are hereditary. The factors for the production of the cranial abnormalities are widespread, but the occurrence of deformities is comparatively rare in a general animal population. In-breeding and selective matings, however, tend to increase their frequency and also the frequency of other abnormalities with which they may be associated, either by chance or by close genetic relationship in the germ plasm. In this way, a pathological complex is built up and perpetuated.
In so far as the cranial abnormalities are concerned, it seems now that oxycephaly and related conditions are variations resulting from a displacement or division of primary ossification centers controlled by hereditary factors.