Fig. 6.

Boxplot representation of measurements taken from male mice for the comparison of fertility. a Number of sperm in the cauda epididymis and (b) the mass of epididymis, testis, seminal vesicle with coagulating gland, and preputial gland were compared between males of the CHBU race, the CHHN race, F₁ hybrids between CHBU and CHHN, and offspring resulting from backcrosses of hybrids to CHHN (see Fig. 4). Offspring from backcrosses were grouped according to their diploid chromosome number (BC.23 for 2n = 23, BC.24 for 2n = 24). The boxplot boundaries indicate the minimum, the first quantile, the median, the third quantile and the maximum. Outliers are shown as circles. The sample sizes are listed below or above the corresponding boxplots. Note that in the male fertility analysis, the category BC.24 includes offspring from fully fertile BC2 and BC3 females (two per female)