ABSTRACT In ‘Reichert’s Archiv ‘for I860,’ part 1, M. A. Baur has published an interesting memoir on the chitinous tendons of Articulata, and their relation to the change of skin. The simplest and oldest view of these structures regarded them as being nothing more than inward prolongations of the outer skeleton, resembling true tendons, but not as corresponding to those of the Vertebrata, which consist of connective tissue. Leydig, on the other hand, considers that these tissues do correspond to one another, and that, while the tendons of Vertebrata often become bony, those of Articulata tend to change themselves into chitine.