I attempt to explain what Heidegger means by the expression "the transformation of the biographical data in the poem" in his elucidation of the Holderlin's hymn Remembrance. Many scholars of German literature are interested in the date of the hymn and in Holderlin's experience at that date, in order to interpret the hymn. In contrast to them, Heidegger does not concern himself with the date, because he believes that the poet's biographical data has nothing to do with the content of the poem directly. According to Heidegger, the transformation of the biographical data in the poem takes place through a process of poeticizing. Therefore, I investigate this process as the nature of the poetry. For this investigation, I refer to Heidegger's elucidation of the hymn As When on Holiday..., which he regards as the "purest poem on the essence of poetry". Afterwards, I interpret the hymn Remembrance in view of the "mariners", which Heidegger calls "Germania's coming poets". This interpretation serves to help us understand the transformation that occurs in the process of poeticizing.