Determination of the First Two Cleavage Furrows in Developing Eggs of Triturus Alpestris Compared with Other Forms

Eggs of Triturus alpestris were horizontally compressed at times before first and second cleavage in an experiment designed to measure the time at which the mitotic apparatus determines the direction of the subsequent cleavage furrow. The results showed that furrow determination was completed 0.46 Dettlaff units before the onset of furrowing. When a comparison was made of the times of furrow determination before cleavage in eggs of different animal groups using Dettlaff units, the results supported the idea that preparations for furrowing proceed differently in echinoderm eggs from eggs of sturgeon and amphibia.