When the eggs first exit the uterus of their mother, they are composed solely of yolk granules. Over a period of 72 hours, the eggs undergo mitotic division into two blastomeres that are separated by a transverse cleavage. Two additional cleavages occur within at least 96 hours, so that the eggs are now composed of four cells each. Cellular division continues in this manner and the morula stage is reached within the next week. After a total of 21–22 days, the larvae become fully developed and will not hatch until ingested by a host. The larvae can live for a total of six months without the assistance of a host. The timeline of egg development can vary depending on the species.