Asexual reproduction in which the parent cell divides to produce two daughter cells, each daughter retaining half the parent theca, at least temporarily. During desmoschisis, the theca undergoes fission along a predetermined suture between thecal plates. The fission suture is oblique, usually from the top left to the bottom right (as in oblique binary fission). See also eleutheroschisis. Refer to Text-Figure 5.