Galactogen has been reported in the albumen gland of pulmonate snails such as Helix pomatia, Limnaea stagnalis, Oxychilus cellarius, Achatina fulica, Aplexa nitens and Otala lactea, Bulimnaea megasoma, Ariolimax columbianis, Ariophanta, Biomphalaria glabrata, and Strophochelius oblongus. This polysaccharide was also identified in the Caenogastropoda Pila virens and Viviparus, Pomacea canaliculata,  and Pomacea maculata.
In adult gastropods, galactogen is confined to the albumen gland, showing a large variation in content during the year and reaching a higher peak in the reproductive season. During the reproductive season, this polysaccharide is rapidly restored in the albumen gland after being transferred to the eggs, decreasing its total amount only after repeated ovipositions. In Pomacea canaliculata snails, galactogen would act, together with perivitellins, as a main limiting factor of reproduction. This polysaccharide has been identified in the Golgi zone of the secretory cells from the albumen gland in the form of discrete granules 200 Å in diameter. The appearance of galactogen granules within the secretory globules suggests that this is the site of biosynthesis of the polysaccharide.
Apart from the albumen gland, galactogen is also found as a major component of the perivitelline fluid from the snail eggs, comprising the main energy source for the developing embryo.