THE fourth part of the Bulletin of the National Academy of Sciences recently founded at Cordova, in the Argentine. Republic, completes the first volume of this remarkable work, of which we have previously given some account to our readers.† The present part is mainly occupied by the conclusion of a long article upon the vegetation of the little known province of Tucuman, in the interior of the Republic, by Dr. Hieronymus, commenced in a former number. This is based upon the observations made by the author during a long and extensive scientific journey in that province, and upon the collections amassed by Dr. Lorentz in the same districts in 1871 and 1872, which have been mainly determined by Prof. Grisebach, of Göttingen. A second important article is by Dr. D. A. Döring, and treats of the land and freshwater Molluscs of the Argentine Republic, amongst which are a considerable number of new species, and several interesting novel forms discovered by the author. A third memoir, from the pen of Dr. Burmeistet, treats of the abnormal Hymenopterous insects of the Linnean genus Mutilla, and forms a complete monograph of the native species of this group, which will be very acceptable to entomologists. By the chronicle appended to the number, we learn that the strife which has prevailed between the Director of the Academy and the six German professors originally imported for its constitution has terminated in the signal defeat of the latter. After the expulsion of about half the number, the remainder resigned, and their places have been filled by other professors from the same country, whom we trust Dr. Burmeister will find more tractable. That they are full of work is evident by the contributions to science already published in the present volume, upon the successful completion of which we heartily congratulate the energetic and illustrious Director of the Academy of Natural Sciences of the Argentine Republic.