Board Thread:Warhammer 40k General Discussion/@comment-2.221.112.151-20130917212029/@comment-92.231.19.119-20131006143629

As I remember correctly the progenoid glands hold the genetic information about the Astartes that carried them. With the collected information the chapter can create the zygotes (also known as gene-seed), which are the basis for each Astartes implant. These zygotes can be created en masse, which is shown by the fact that each and every chapter has to send probes of their gene-seed to the Adeptus Administratum I think. (Not doing this was a start for the Badab War)

I think that the freshly collected progenoids show the qualities of an Astartes in his chapter and can make him immortal by collecting his data. As another aspect they show the current status of the chapter's gene-seed, whether it is flawed or even mutating to a degree one could call heretic.