If an old culture or its "metabolic products" are introduced into the body of animals, within them there occurs a union of the zymase with the body albumin-immunproteïdin (Emmerich). These immunproteïdins have the same solvent action upon bacteria as the bacteriolytic enzymes, but are more durable and, above all, more capable of persisting in the blood. At least in some infectious diseases the immunproteïdins can be produced synthetically in vitro instead of in the animal body, and thus, according to Emmerich and Löw, materials may be produced rapidly and cheaply which possess very high immunizing power. The immunproteïdins operate also much more strongly anaerobically than aerobically. The difference between the Gruber-Durham reaction (agglutination without death) and the R. Pfeiffer reaction (death in the abdominal cavity) is essentially dependent upon the following: In the peritoneal cavity a scarcity of oxygen prevails and the peristalsis mechanically disturbs the agglutination; also, Emmerich and Löw find the bactericidal action of normal blood to be dependent upon enzymes.

This mass of observations, which are most worthy of notice, is not to be overlooked to-day, although there has been no opportunity for substantiating them. If they prove true, they render an essential revision of the whole question of immunity necessary.

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Summarized presentations regarding immunity or of the greater part of the subject are: Buchner, H., Schutzimpfung, etc., in Handbuch der Therapie," Jena, 1897. Metschnikoff, "Immunität," Jena, 1897. Trumpp, A. H. XXXIII, 70. Dieudonné, "Experimentelle und kritische Beiträge zur Kenntnis deragglutinieren den Stoffe, etc." Habilitationsschrift. Würzburg, 1898. Dieudonné, "Schutzimpfung und Serumtherapie." Leipzig, zweite Aufl., 1899.

A. Introduction to the Classification of

Fission-fungi.

I. The Fundamental Ideas of Botanical Classification Applied to Fission-fungi.

All individual plants which upon careful examination are alike and transmit their characteristics to their descendants are designated as representatives of a botanical variety (species).

A

The nomenclature of the animal and vegetable kingdoms employed at present is founded upon the assumption that a very definite number of varieties of plants (species) are present upon our planet which can certainly be distinguished from each other by characteristics visible with more or less ease, and which, through propagation, reproduce themselves unaltered in all essential characteristics. number of such species possess certain common characteristics and thus exhibit a certain close relationship,-these species are placed together in a genus. As genus characteristics it is only allowable in general to select actual characteristics, usually those concerning the structure of the organs of reproduction. Some genera consist of single species, others include hundreds. A group of genera forms a family.

In certain groups of the vegetable kingdom the actual circumstances suit this scheme very well. The individuals can be divided easily into a number of sharply characteristic varieties, not connected by any transition; a number of varieties group themselves naturally into a genus, and the genera constitute a natural, sharply defined family. The conditions are nearly so in the case of the German malvacea. The family is sharply characterized; it consists of four genera, and each genus includes from one to