ahierarchy of species and genera to see the great gain that has been effected. It is the very nature of fixed kinds to be as exclusive with respect to those of adifferent order as it is to be inclusive with respect to those which fall within the class. Instead of athoroughfare from one order to another, there was asign: No passage. The work of emancipation which was initiated by experimentation, setting objects free from limita- tion by old habits and customs, reducing them to acollection of data forming aproblem for inquiry, is perfected by the method of conceiving and defining objects through operations which have as their consequence accurate metric statements of changes correlated with changes going on elsewhere.