The Progenoid Glands, also known as the Gene-Seed, are the 18th of the 19 genetically-engineered gene-seed organs implanted within an adolescent Space Marine Neophyte to create a new Astartes. Every Space Marine has these organs, one implanted in the neck and another in the chest. The organs hormonally respond to the presence of the other Astartes gene-seed implants in the body by creating germ cells with DNA identical to that of those implants through a process very similar to cellular mitosis. These germ cells grow and are stored in the Progenoid organs, much like sperm cells or egg cells are stored in the testes and ovaries of normal men and women. When properly cultured by the Apothecaries of a Space Marine Chapter, these germ cells can be gestated into each of the 19 gene-seed organs needed to create a new Space Marine. Thus, for most Astartes, their Progenoid Glands represent the only form of reproduction they will ever know, though the DNA passed on will be that of their Primarch, not their own. Mature Progenoid organs can be removed and new gene-seed implants artificially cultured from them. This is the only way new implants can be created, so a Chapter depends upon its existing Space Marines to create other Space Marines. Five standard years after implantation, the Progenoid Gland in the neck contains mature gene-seed and may be removed and its germ cells harvested, while the larger chest Progenoid is not considered ready for harvesting until 10 standard years have passed. The harvesting is normally done after an Astartes' death by an Apothecary, who carries a special attachment on the mobile medical field kit he carries on his arm known as a Narthecium. This attachment is called a Reductor and it is specifically used to extract both Progenoid Glands from the body of a slain Asartes so that his gene-seed can be used to replace the Chapter's loss, the only form of true immortality that Astartes will ever know.
Just like normal human germ cells, exposure to high concentrations of ionizing radiation can effectively render a Space Marine "sterile" by destroying the germ cells within his Progenoids. Over the long millennia since the Space Marine Legions were first founded, a Space Marine Chapter's gene-seed can also mutate, producing new and hitherto-unknown physiological effects in that Chapter's Space Marines or simply becoming non-functional. Repeated exposures to the corrupting energies of Chaos can also cause mutation within the gene-seed. This is why every Chapter's gene-seed is required to be monitored for mutations and genetic purity by the Tech-priests of the Adeptus Mechanicus and why every Chapter is required to tithe 5% of its gene-seed stocks at regular intervals to the Mechanicus on Mars. This is done both to check for purity and to be used to create new Space Marine Chapters if the High Lords of Terra call for a Space Marine Founding.
Known Gene-Seed Flaws
- Blood Angels - Black Rage and the Red Thirst
- Imperial Fists - Betcher's Gland and Sus-an Membrane are no longer functional
- Space Wolves - Enlarged canine teeth, extreme hirsuteness and possibility of mutational degeneration into a Wulfen
- Raven Guard - The Mucranoid and Betcher's Gland are no longer functional. Raven Guard Astartes often develop extremely pale skin and their hair turns black, regardless of their original complexion or colouration.
- Blood Ravens - The Blood Ravens can no longer expereince true REM sleep and so they cannot dream, and after they are implanted with their gene-seed organs, they possess perfect recall of every event for the rest of their lives. Blood Ravens Astartes also seem to develop psychic abilities at an unusually accelerated rate.
- Salamanders - The Melanochrome has mutated and no longer functions properly, producing onyx black skin and blazing red eyes in every Salamanders Astartes.
- Blood Drinkers - The Blood Drinkers' gene-seed, drawn from Sanguinius just like that of the Blood Angels, has further mutated, leading to a worsening of the Red Thirst Flaw in which the Blood Drinkers suffer an overriding thirst to ingest the blood of their enemies in order to stop the cravings. Unlike the Blood Angels and their other Successor Chapters, these cravings afflict the entire Chapter and not just those who fall to the Red Thirst. This has led to the development of Chapter-wide blood drinking rituals which both provided the Chapter with its name and keeps the blood-lust in check.
- Thousand Sons - This Traitor Legion's gene-seed, drawn from the Primarch Magnus the Red, was always genetically unstable and prone to rapid mutation, leading to the development of psychic powers in the majority of Thousand Sons Astartes but also to a terrible mutational degeneration into what would later be recognised as Chaos Spawn and was known as the "Flesh-change." The Blood Ravens may be the Loyalist descendants of the Thousand Sons which would explain both their unusual psychic abilities but also their tendency to be easily corrupted by Chaos.
Chaos Space Marines
The Traitor Legions of Chaos Space Marines also all possess Progenoid Glands, which could be harvested to create new Astartes. The problem is that their constant exposure to the corrupting energies of Chaos, particularly for those Traitor Legions that now live within the Eye of Terror where exposure to Chaotic energies is constant and intense, often leads to the complete mutational degeneration of the gene-seed. The problem has become so acute that many Chaos Space Marine warbands now seek to raid Loyalist Space Marine gene-seed repositories so that they might be able to replenish their Legions' losses over the last 10,000 standard years since the Horus Heresy.
- Codex: Space Marines (5th Edition)