Study Hall - Shobogenzo

Just as time flows forwards and backwards, and just as mountains flow, the transmission of the teaching is not simply how it appears to be. In 'Buddha Ancestors' and 'Document of Heritage', 'Busso' and 'Shisho', Dogen looks at the lineage, and the transmission documents that he was able to see in China. When he sees the documents offered by Abbot Yuanzi, in Damei's lineage, he says, touchingly, "Tears wet my sleeves" as he realised his good fortune in having such an opportunity, and he dreams of Damei and plum blossoms, just as the Abbot had before Dogen's arrival, and writes "This dream was as real as being awake. I have never before told this story to anyone in China or Japan". 
But while he insists on the documents, just as he insists on the robe, as the emblem of the authentic teaching, he does not limit this to a linear transmission; he quotes his teacher Rujing saying "Because of this heritage from buddha to buddha until now, each buddha is an heir. Buddhas are not lined up, nor are they gathered together, but they just inherit from each other...We understand that Shakyamuni Buddha received dharma from Kashyapa Buddha, and Kashyapa Buddha received dharma from Shakyamuni Buddha. When you understand in this way, it is the true dharma heritage of all buddhas and ancestors".
In the kechimyaku blood vein lineage papers that we receive here at Zen Center, this is represented by the line that connects the teacher and disciple returning to an empty circle above Shakyamuni. Here is the one I received at my tokudo, which I just unfolded for the first time: