Abstract
When a female of Bombyx mori is mated with two males of different genic constitution one after the other, two different kinds of offspring, corresponding to the paternal characters, are produced. In such a mating, the number of the offspring of the first mated male generally tend to be predominant (Tables 2 and 4b).
The monstrous male having a recessive mutant character, monstrum abdominis, which was obtained by Ômura and Sinohara (1937) (Fig. 1), has shown nothing unusual in fertility when it was ordinarily mated with the female (Table 1). An unexpected result, however, was obtained from a double mating experiment made with this monstrous male and a ordinary male. An extremely low fertility was demonstrated, nearly 0% for the former, even when it was used as the first male in the mating (Table 3). Further data shown in Table 4 indicate decisively that the fertility of the spermatozoa of the monstrous male is extremely reduced when mixed with the spermatozoa of the ordinary strain.
For the explanation of these facts a selective fertilization between the spermatozoa of the monstrous strain and those of the ordinary strain is most likely responsible. Judging from the behavior of the spermatozoa in the female genital organs (Ômura 1938) and from the results shown in Table 4a, it is probable that certain kinds of processes concerning selective fertilization may take place in the egg cell where polyspermy normally occurs (Kawaguchi 1926). Several problems associated with the selective fertilization here concerned are left for further investigation.
