Membranes are consistent components of spindles in plants and animals. Depending on the species, they either form layers at the periphery of the spindle, are scattered throughout the spindle area or can be observed in both locations. This review aims to provide a survey of the arrangements and functions of membranes associated with the spindle apparatus in diverse invertebrate groups. In order to make the reader familiar with the architecture of the spindle apparatus and the course of nuclear division, centrosomes, microtubules (MTs) and centromeres are briefly introduced, the issue of membrane structure is addressed in general terms and orthodox as well as unorthodox cases of genome separation are described. As regards function, spindle membranes are believed to play a role in the control of progression of nuclear division through the release and sequestration of Ca 2 + ions. In fact, there is evidence that membrane-bound, intra-spindle compartments sequestrate Ca 2 + ions and it is beyond doubt that spindle microtubules are sensitive to Ca 2 + ions. It is tempting to correlate both features, but cogent evidence for this link has still to be produced. In invertebrates, there are findings that raise the possibility of additional and alternative functions for spindle membranes: (i) the control of the interaction between MTs and chromosomes, (ii) the nucleation of MTs, (iii) a storage site for material used in later stages of development and (iv) a direct effect on the MT mass within the spindle through volume exclusion. Thereby, the concentration of tubulin monomer, the precursor of MTs, is raised and MT assembly is fostered. Finally, the possibility should not be overlooked that perispindle membranes prevent the entry of cytoplasmic elements into the spindle area and that the association with the spindle apparatus ensures the approximate bipartition of the cytoplasmic membrane inventory during cell division.