The fact that the living cell grows after taking up food has given rise to curious misunderstandings. Traube has shown that drops of a liquid surrounded with a semipermeable membrane may increase in volume when put into a solution of lower osmotic pressure. This has led and is possibly still leading to the statement that the process of growth by a living cell has been imitated artificially. Only one feature has been imitated, the increase in volume; but the essential feature of the process in the living cell, _i. e._, the formation of the specific constituents of the living cell from non-specific products, has of course not been imitated. 4. The constant synthesis then of specific material from simple compounds of a non-specific character is the chief feature by which living matter differs from non-living matter. With this character is correlated another one; namely, when the mass of a cell reaches a certain limit the cell divides. This is perhaps most obvious in bacteria which on the proper nutritive medium take up food, grow, and divide into two bacteria, each of which takes up food, divides, and grows _ad infinitum_, as long as the food lasts, provided the harmful products of metabolism are removed. If it be true that specific synthetic ferments exist in each cell it follows that the cell must synthetize these also,[22] as otherwise the synthesis of specific proteins would have to come to a standstill. [22] This would lead to the idea that the enzymes in the cell also synthetize molecules of their own kind, or that, in other words, the synthetic processes in the cell are of the nature of autocatalysis. Loeb, _Der chemische Character des Befruchtungsvorgangs_, Leipzig, 1908. Robertson, T. B., _Arch. f. Entwicklngsmech._, 1908, xxv., 581; xxvi., 108; 1913, xxxvii., 497; _Am. Jour. Physiol._, 1915, xxxvii., 1; Robertson and Wasteneys, H., _Arch. f. Entwicklngsmech._, 1913, xxxvii., 485. Ostwald, Wo., _Über die zeitlichen Eigenschaften der Entwicklungsvorgänge_, Leipzig, 1908.