Proliferation, growth, and migration of nuclei the yolk syncytium of Salmo and Catostomus

Nuclei of the yolk syncytial layer (YSL) were counted, measured, and mapped at several stages of morphogenesis selected representatives of the Clupeiformes and Cypriformes. The data show coordated motion of nuclei before and durg morphogenetic movements of the cellular blastodisc. This motion may be used to trace cytoplasmic flow the syncytium at early stages. The data show that YSL nuclei proliferate mitotically at first. Further proliferation, after mitosis ceases, happens by an unknown mechanism. Growth of YSL nuclei Salmo gairdneri does not occur by fusion of smaller nuclei as others have suggested for teleosts. The matter is still unsetted for Catostomus commersoni .