Abstract
Summary
1. The frequency of mid-mitotic neuroblasts in grasshopper embryos in hanging-drop cultures increases as the quantity of yolk in the culture is increased up to a quantity equivalent to 1/4 that in an egg. The influence of yolk on mitosis in the untreated neuroblast is interpreted as indicating that, in this cell at least, the first half of prophase does not operate solely on energy stored within the cell but is dependent on an outside source of energy for continuance of mitosis. 2. The pronounced positive effect of yolk on recovery of neuroblasts from radiation damage demonstrates that, in this cell, some extracellular metabolite or metabolites greatly enhance repair of mitotic damage.
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