The cristae ampullares of 16 guinea pigs were examined after their arrangements, weights and figures as after their relations to each other. It was noted that the size of the single crista increased from lateral to medial. They are inproportional to their related bony canals. Both the front cristae developed from the same basal plate and they are by the guinea pig less developed than the crista at the back. These different expansions of the cristae are considered in relation to the phylogenetical developement of the three canals. Where the size of the sensory cells by all the cristae ampullares are nearly the same, we fined that their number vary significantly. The expansions of the ampullares were we fined the cristae are confined to the membranous labyrinth. The bony labyrinth does not participate in that expansion. The supporting cells are of a great functional importance. Probably they transmit the required energy which they get from the lymph as well as the near by capillaris. Beyond that the sensory cells are able to support themselves directly with difinite nutriments from the endolymph.