"When the genetic material of a highly virulent bacteriophage penetrates a bacterium, the bacterial chromosome is disintegrated and the bacterium consequently becomes incapable of producing messengers and bacterial proteins. The DNA of the bacteriophage synthesizes its own messengers with the aid of s synthesized by its host and of the enzymes of its host. The messengers of the bacteriophage will establish themselves on the bacterial s. With the aid of the activated and of the bacterial enzymes, the proteins of the bacteriophage are synthesized. Some of these proteins are enzymes necessary, for example, for the manufacture of specific constituents of the phages such as . Others are enzymes necessary for the replication of the bacteriophage DNA. Still others are structural proteins of the . One of the last to be formed is endolysine, which destroys the wall of the bacterium, provokes its rupture, and ensures the liberation of the virions. When we examine the kinetics of production of the various proteins, we find that each is formed in a given period of the evolutionary cycle. Everything takes place as if a system of sequential repression and derepression was acting."