Alcorn 1939. Dipodomys ordii columbianus /mi. N Soda Lake, 4000 ft., Churchill Co., Nevada. April 19 1939. 17 ♂'s with 25 ♀'s picked up as follows after poisoning operations. 2 ♀'s had 4 embryo ⅔ developed. (Each ♀ had 4) 2 ♀'s had 4 embryos ½ developed "" 1 ♀ had 4 embryos ⅔ developed with 5 embryos dead in uterus 1 ♀ had 4 embryos 7 mm. diameter (Each ♀ had 4) 4 ♀'s had 3 embryos ⅔ developed (Each ♀ had 3) 1 ♀ had 4 embryos ⅓ developed 2 ♀'s had 3 embryos each, ⅓ developed 0 ♀'s had enlarged uterus horns 8 ♀'s were being suckled, recently given birth to young. 4 ♀'s had normal mammae + uterus horns. April 21 1939. 5 ♂'s and 3 ♀'s picked up today follows: 1 ♀ with normal mammae + uterus horns 2 ♀'s being suckled, enlarged mammae.