On the inverted eggs observed in ovarioles of pupae in the silkworm, Bombyx mori

Abstract

In the previous paper, one of the authors (Totani, 1970) reported that some inverted eggs were observed in ovarioles of 7-day-old silkworm pupae of N 131, a Japanese variety. In this paper a further study of the inverted eggs is dealt with.
The inverted eggs are distinguished by their micropyle-anterior position from normal micropyle-posterior ones in ovarioles and always accompanied by conjoined eggs which are located in the adjacent position toward the upper part of them (Plate I).
Two conjoined eggs in the same cavity consit of a normal oocyte and seven nutritive cells, respectively, and are separated from each other by the folicular epithelium or chorion (Plate II).
Some conjoined eggs were found amongs normal eggs deposited on egg cards (Table 1 and Plate III).
The number of inverted eggs and the distribution of them differ with ovarioles even in the same individual.
Moths of N131 in which the occurrence of inverted eggs was more frequently. found laid more eggs invertedly than those of the other varieties examined.