The Bavli, Shabas 22 amud 2, notes that כיון דקביעי נרות לא סגיא דלא משקיל ואדלוקי, since the lamps (receptacles for oil) were affixed to the m'nora in the bes hamikdash, there was no way to transfer a flame from one lamp to another except by means of an intermediary such as a spill. Nonetheless, Rashi on that very page, describing how the kohen prepared the m'nora, says that one lamp would remain lit (miraculously) until it was time to re-light the m'nora, so ואוחז הישנה בידו או מניחה בכלי עד שנותן שמן ופתילה ומדליקה, the kohen held that light in his hand or in a receptacle until he had put new oil and a wick in the lamp, then lit the lamp from that light. Riva, quoted in Tosafos there, asks the obvious question: שאם אפשר להדליק מן הישנה א״כ גם השאר ידליק ממנה ומאי פריך לרב, if it's possible to do as Rashi describes then why does the g'mara say there was no way to transfer a flame from one lamp to another without a spill? Tosafos have no answer to this question on Rashi. Does anyone?
Tosfos in Menachos 86b ד"ה ממנה writes in the name of Rabenu Tam ( see also Chudishei HaRan ד"ה ובא ) that Rashi holds that there is a mitzvah to have in the menorah a fixed ner to light the remaining six. This is learned from the pasuk להעלות נר תמיד (שמות כז כ. Therefore after the ner maarivi is lit from the the old flame the remaining neros are lit from the ner maaravi and this must be achieved with a kisem.