Abstract
The present paper is to report the results of some preliminary observations on hormone-induced superfecundity in mature and immature mice, with special reference to the number of young.
The mice used are of D-240 strain: they are 60 and 35 days in age. The average litter size from 82 litters of this strain was found to be 6.5, with a range from 2 to 12.
The mice in various stages of oestrus cycle received an intramuscular injection of 5 I. U. pregnant mere's serum "Serotropin" (Teikoku Hormone M. F. G. Co.), a follicle stimulating hormone. After about 40 hours, the animals were injected again with 10 I. U, human chorionic hormone "Primogonyl" (Schering A. G.). After treatments the mice were mated by being placed with males at the rate of one female to three males. On the following morning, the females were inspected for presence of the copulatory plug in their vaginas, and some of them were sacrificed for examining superfecundation.
The number of new-born young obtained in this experiment was 63 in total; they vary from 11 to 15 by individual, being 12.6 on an average (Table 1).
The results are striking in showing a remarkable superfecundation, on the basis that the number of young in control was 6.5 on an average.
