THE DEVELOPMENT OF CYTOPLASMIC BRIDGES IN VOLVOX AUREUS

Abstract

The structure and development of cytoplasmic bridges connecting adjoining cells in Volvox aureus coenobia is demonstrated by electron microscopy. The cytoplasmic connections originate from incomplete cell division. In the early stages, mitochondria and other smaller organelles may move freely from one cell to the next. The cytoplasmic bridges then stretch as the cells separate from each other during maturation of the colony. When they are fully stretched, only endoplasmic reticulum and ribosomes are found in these cytoplasmic strands. The nature of these cytoplasmic connections is discussed and it is concluded that they should be distinguished from plasmodesmata of higher plants and the structures should be called simply "cytoplasmic bridges". It is also reported that the matrix of the colonial wall is derived from the dictyosome activity during the coenobium development.