Bdelloids reproduce via obligate apomictic parthenogenesis. Oogenesis occurs through two subsequent equational divisions, with the extrusion of two polar bodies. Although the morphology of the bdelloid reproductive apparatus has been previously described, the eutely of the germarium has never been investigated. We studied oogenesis in Macrotrachela quadricornifera by assessing: (1) the constancy of oocyte number, (2) chromosome number and size, and (3) the DNA content of oocytes and blastomeres. Oocyte number at birth is constant and determines minimal fertility. We found a chromosome number of S, in which two homologous pairs can be recognized. The genome size of the species is 0.75 picograms