Reproduction in some Pinnipedia.



  • 1The reproductive organs have been described in a series of seals, including foetal, neonatal and adult specimens. The collection includes seals from the Antarctic, European waters and from the North Pacific. The species are:—Leptonychotes weddelli, Lobodon carcinophagus, Hydrurga leptonyx, Phoca vitulina, Halichoerus grypus, Otaria byronia. Zalophus californianus, Eumetopias stelleri, and Callorhinus ursinus.
  • 2The gross and histological appearances of the testis are described. There is evidence of a breeding season and cyclic testicular activity in the Wed dell and Crabeater Seals. Some measurements of the os penis are given.
  • 3A description is given on the gross anatomy of the urinogenitai tract in the female. The ovarian bursa is much enlarged during pregnancy. The urinary papilla is large, partly owing to the presence of lymphoid tissue.
  • 4Unimplanted blastocysts have been found in the Crabeater Seal at a time that confirms the occurrence of delayed implantation. Other evidence suggests that delayed implantation is universal in most, if not all, seal.
  • 5In at least two species, the Grey and Common Seals, there is marked enlargement of the late foetal and neonatal gonads to a size near or surpassing that of the maternal gonads. This enlargement is primarily due to an increase in the volume of interstitial tissue.
  • 6Invaginations of the epithelium forming sub-surface crypts have been observed in all species of pinniped examined. There is evidence of cyclical activity in the number and development of these crypts. Their relationship to oogenesis is discussed.
  • 7The changes in the corpus luteum are described during early and late pregnancy. During the period of delay in implantation the majority of the luteal cells are heavily vacuolated.
  • 8The changes in the uterus and vagina are correlated with the changes in the ovary, both in the foetal, neonatal and adult. Coiling of the uterine glands and secretory activity is found in the neonatal specimens.
  • 9A short note is appended on the foetal membranes.