Abstract
1. Early divisions of yolk cells in vitro were observed in Bombyx mori.
2. At the beginning of the yolk cell formation, many large multinuclear cells or masses of yolk are seen dividing gradually into smaller ones which contain lesser number of nuclei, and completed yolk cells are for the most part mononuclear accompanied with some multinuclear ones.
3. In the course of these divisions the yolk cells show marked variations in shape which are strange to us as compared with the ordinary roundish or ovalish shape (resting form) of them.
4. The whole of yolk cells is hardly understandable without the recognition that they are variable and living units which can move, divide and make groups in vitro, showing marked variations in shape. These activities may possibly be manifested also, in some degree, in vivo.
5. The plasma connection remaining between separated yolk cells may have some relation to the origin of the peculiar satellitic body of moving yolk cells.
6. The author's opinion was stated about the terminologies of yolk nuclei and yolk cells.
