However , in dinoflagellates , the nuclear envelope remains intact , the centrosomes are located in the cytoplasm , and the microtubules come in contact with chromosomes , whose centromeric regions are incorporated into the nuclear envelope ( the so @-@ called closed mitosis with extranuclear spindle ) . In many other protists ( e.g. , ciliates , sporozoans ) and fungi , the centrosomes are intranuclear , and their nuclear envelope also does not disassemle during cell division .