Students in a cognitive/computer science class posted blog entries at the rate of two per week and commented on each others contributions. The co-blogging work of the students provided the opportunity to reflect upon and discuss the course materials and lectures and thereby develop their understanding of the topics and themes of the course. The discussion of certain topics continued throughout the semester, with students referencing earlier posts, examples, arguments, and explanations as the conversation progressed. This poster presents a visualization that depicts the flow of ideas within the online community over the semester. Key notions of the analysis are seeding, anchoring, and persistence: conversations of new material were seeded with earlier blog content, prior posts and comments anchored the discourse, and "common" understanding was mediated by persistent external representations.