The general organization of the vitellocytes inAllostomasp. is described. In all the species of prolecithophorans studied, and therefore also inAllostomasp., the eggshell globules have the same ultrastructure consisting of highly electron-dense granules embedded in a medium-electron-lucent grey matrix (multigranular pattern) and mainly contain polyphenols. The type of yolk bodies principally characterized by membrane whirls inAllostomasp. is unknown for the other neoophoran taxa. This peculiar yolk originates from Golgi-derived vesicles, presumably containing lysosomal enzymes, which fuse with membrane-bound substrates. This characteristic is hypothesized as an autapomorphy of the Prolecithophora.