POST HATCHING AND POST-PARTUM CARE OF YOUNG 



931 



phase. The first phase in the North American opossum consumes about 13 

 days, and the latter about 50 days. After the young become free from their 

 nipple attachment they spend about 40 days in and out of the marsupium. 



Bibliography 



Anderson. D. H. 1927. The rate of pas- 

 sage of the mammalian ovum through 

 various portions of the Fallopian tube. 

 Am. J. Physiol. 82:557. 



Asmundson, V. S. and Burmester, B. R. 

 1936. The secretory activity of the parts 

 of the hen's oviduct. J. Exper. Zool. 



72:225. 



Eigenmann, C. H. 1892. On the viviparous 

 fishes of the Pacific coast of North 

 America. Bull. U. S. Fish Commission, 

 Vol. 12:381. 



Engle, E. T. 1939. Gonadotropic sub- 

 stances of blood, urine, and other body 

 fluids. Chapter 18, Sex and Internal Se- 

 cretions. Ed. by Allen, et al., Williams 

 & Wilkins, Baltimore. 



Flynn, T. T. and Hill, J. P. 1939. Part 

 IV: Growth of the ovarian ovum, mat- 

 uration, fertilization, and early cleavage. 

 Trans. Zool. Soc. London. 24 Part 6:445. 



Hertig, A. T. and Rock, J. 1945. Two 

 human ova of the pre-villous stage, hav- 

 ing a developmental age of about seven 

 and nine days respectively. Carnegie Inst. 

 Publ. No. 557. Contrib. to Embryol. 

 31:65. 



Hisaw, F. L. and Albert, A. 1947. Obser- 

 vations on reproduction of the spiny 

 dogfish, Squaliis accmthias. Biol. Bull. 

 92:187. 



Kerr, J. G. 1919. Textbook of Embryol- 

 ogy, Vol. II, The Macmillan Co., London. 



Kupperman, H. S., Greenblatt, R. B., and 

 Noback, C. R. 1943. A two- and six- 

 hour pregnancy test. J. Clinical Endo- 

 crinol. 3:548. 



Lewis, W. H. and Wright. E. S. 1935. On 

 the early development of the mouse egg. 

 Carnegie Inst. Publ. Contrib. to Embryol. 

 25:113. 



McCrady, E., Jr. 1938. The embryology of 

 the opossum. The American Anatomical 

 Memoirs, No. 16. The Wistar Institute 

 of Anatomy and Biology. Philadelphia. 



Mossman, H. W. 1937. Comparative mor- 

 phogenesis of the fetal membranes and 

 accessory uterine structures. Carnegie 

 Inst. Publ. No. 479. Contrib. to Embryol. 

 26:129. 



Noble, G. K. 1931. The Biology of the 

 Amphibia. McGraw-Hill Book Co., New 

 York. 



Romanofi', A. L. and Romanoff", A. J. 

 1949. The Avian Egg. John Wiley and 

 Sons, New York. 



Scrimshaw, N. S. 1944. Embryonic growth 

 in the viviparous poeliciid, Heterandria 

 fonnosa. Biol. Bull. 87:37. 



Siegler, S. L. and Fein, M. J. 1939. Studies 

 in artificial ovulation with the hormone 

 of pregnant mares' serum. Am. J. Obst. 

 & Gynec. 38:1021. 



TeWinkle, L. E. 1941. Structures con- 

 cerned with yolk absorption in Squalus 

 acanthias. Biol. Bull. 81:292. 



. 1943. Observations on later phases 



of embryonic nutrition in Squalus acan- 

 thias. J. Morph. 73:177. 



1950. Notes on ovulation, ova, and 



early development in the smooth dog- 

 fish, Mustelus canis. Biol. Bull. 99:474. 



Wiltberger. P. B. and Miller, D. F. 1948. 

 The male frog, Rana pipiens, as a new 

 test animal for early pregnancy. Science. 

 107:198. 



