Pollen (microsporocyte, pollen mother cell or meiocyte), after meiotic division. After the formation of the four microspores, which are contained by callose walls, the development of the pollen grain walls begins. The callose wall is broken down by an enzyme called callase and the freed pollen grains grow in size and develop their characteristic shape and form a resistant outer wall called the exine and an inner wall called the intine. The exine is what is preserved in the fossil record. Two basic types of microsporogenesis are recognised, simultaneous and successive. In simultaneous microsporogenesis meiotic steps I and II are completed
The X from Outer Space Guilala is finally defeated by jets laden with bombs, which coat it in a substance called "Guilalalium." It causes Guilala to shrink down to its original spore form. The government promptly launches the spore back into space, where it will circle the sun in an endless orbit. "The X From Outer Space" was released in Japan on 25 March 1967. "The X From Outer Space" was never released theatrically in the United States, and was released directly to television by American International Television in 1968. The Criterion Collection released "The X from Outer Space" on DVD in a compilation titled