Fig. 7. Nuclear events and the formation of mitotic asters in a Pattern 3 conjugate. The time (in minutes) after activation is given in the upper right corner of each image. White arrows indicate `aster-like structures'; white arrowheads indicate nuclei; black arrowheads indicate single asters. (A) A pronucleus (PN) forms. (B) The first mitotic cycle. An `aster-like structure' developed at a site where the PN had been located. Two asters emerge, away from the pronuclear site. (C) One nucleus reforms. (D) The second mitotic cycle. Four asters and a single `aster-like structure' develop. (E) One nucleus reforms. (F) The third mitotic cycle forms eight asters and an `aster-like structure'. (G) One nucleus reforms. (H) The fourth mitotic cycle, forms 16 asters and an `aster-like structure'. (I) One nucleus reforms. (a,c,e,g,i) Differential interference-contrast microscopy; (b,d,f,h) polarization microscopy.