The polymerization of Db,!I-phenyl&nine N-carboxy anhydride adsorbed on polysarcosine dimethylamide has been studied further. This unusual reaction, which is analogous kinetically to reactions catalyzed by enzymes, was called the "chain-effect.'' For polymerization of N-carboxy anhydrides by this mechanism it is neceseary that the initiating polymer should posse%s an adsorption site and a terminal base group. The effect is shown to occur with simple compounds such as amino acid dimethylamidea but not with poly-bproline due to the inability of thm polymer to adsorb the anhydride. From a study of the reaction of block copolymers of bproline and earcosine with Dr,@-phenyhlanine it is concluded that the relative positions of the adsorption site and terminal baee group do not greatly influence the reaction rate, but the acceseribility of the adsorption sites is an important factor determining the reactivity of polyearcosine dimethylamidea of various degreea of polymerization (n). At high values of n the polymer exiets in a coiled form, and only those sites close to the terminal base group participate in the reaction. Initial rate studiea give a detailed description of the early stage of the chaiin-effect polymerization. With theee data and by use of analog computer techniques the complete reaction has been studied. It is concluded that the poly-Db@-phenylalanine block produced is not permanently attached to the polyearcosine chain by hydrogen bonds during its formation but that an equilibrium exists between the polyearcosine and the POlY-DL phenylalanine blocks.