3. In a third series of cases, finally, the states have exclusive competence. _They may both legislate and administer._ Of these three hypotheses the one most important from our present point of view is the first. The recognized right of the Reich to have public services designed to apply its laws and acts, permits it to organize public administrations and to have functionaries subordinate directly to the Reich throughout the whole German territory. The unity of the Reich is greatly strengthened by the fact that the principal public services--the army, finances, diplomatic corps, postal telegraphs, railroads--are hereafter completely concentrated in its hands. In addition when the Reich fails to organize its own administration or when it has left to the states the task of legislating on subjects that are contained in the legislative competence of the Reich, the latter is far from being weakened in its power therein. For it possesses in such cases the _Right of Control_ over the administrative authorities of these states, and this right was notably strengthened by the Constitution of 1919 as compared to its former power. According to the terms of Article 15, paragraph 2, control by the Reich may be exercised by the government of the Reich in matters on which the latter has the right to legislate. That means that control on the part of the Reich extends not only to the domains which have been already assigned to it by the legislation of the Reich, but also to matters in which it has the right to legislate even though it has not yet made use of such right. The means by which these rights of control are exercised are the following: (a) General instructions addressed to the authorities of the states for the execution of the laws of the Reich. These instructions of the government of the Reich are compulsory on the different authorities of the states. But instructions to subordinate authorities of these states must not be given in particular applications of these laws, for otherwise these authorities might receive contradictory orders from different sources; and in that way the governments of the state might lose all authority. (b) The control of the Reich is exercised in addition by sending to the governments of the states commissioners charged with the supervising of the execution of the laws of the Reich. Such commissioners may even be sent, with the consent of the governments of the states, to subordinate authorities. In the latter case it must be admitted even that the Reich has the right to demand that the files of the state authorities be opened to it and with the consent of the governments of the states the Reich may examine witnesses, take testimony and make surveys within the provinces of the state. (c) Finally the Reich may demand that lapses observed in the execution of its laws be corrected.