The article is devoted to a formation of a complex speech genre in the culture as a result of borrowing and transformation by changing the basic strategy of the speech genre. The author considers that the processes of assimilation of foreign-language model and the processes of perception and production of the speech are based on the similar principles. The parallelism of the mechanisms shows that the processes of shifts in the model of the genre are consequences of the interference (interaction of genre models not only within a single culture, but of genres from different backgrounds) that leads to the formation of pre-genre. The first unstable model of the assimilated genre needs to be verified in attempts of the different authors to follow the new pattern, which leads to the formation of a new unit in the national system of speech genres. Allocated stages of formation - from a simple copying of the foreign form to the usage of the national cognitive frameworks in realization - delineate the process of adaptation of the complex speech genre in another culture. As an example, the author gives the trajectory of the formation of the genre of the essay in Russia in XX-XXI centuries. The article briefly touches upon the retrospection of the formation a complex speech genre of the Internet blog.