Ultrastructural evidence for the absence of premelanosomes in eggs of the albino mutant (ap) ofXenopus laevis.

The so-called ap mutant strain ofXenopus laevis, which shows periodic albinism during its life cycle, produces batches of fertilized unpigmented eggs of high viability. These eggs were prepared for transmission electron microscopy. Evidence is presented that mature melanosomes as well as premelanosomes are lacking in the eggs. The absence of pigment might be useful as a cell marker in further experimental studies.