The family : an ethnographical and historical outline with descriptive notes, planned as a text-book for the use of college lecturers and of directors of home-reading clubs / by Elsie Crews Parsons.

  • Parsons, Elsie Worthington Clews, 1874-1941.
Date:
1906
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: The family : an ethnographical and historical outline with descriptive notes, planned as a text-book for the use of college lecturers and of directors of home-reading clubs / by Elsie Crews Parsons. Source: Wellcome Collection.

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    22 The Family species the females are viviparous. Among the fe¬ males of a great many species of amphibia, external sac-gestation is the rule. In several species the male helps to place the extruded eggs in the hatching sacs. With one exception, internal fertilisation characterises the class of reptiles, and the higher species are vivipar¬ ous. A few species of oviparous snakes incubate their eggs. Among birds the incubating habit is fully developed. The lowest species scrape holes in the sand for their eggs, and the males are the sole or chief brooders. Many of the young of the higher species are hatched blind, all are hatched naked and depend¬ ent upon their parents for warmth and nourishment. The young of mammals are born, after a more or less prolonged period of gestation, still more helpless. The females of certain species of marsupials, an order low in the class, carry and suckle their young in ab¬ dominal pouches for several months after birth. In the higher orders of mammals, the characteristic pro¬ cess of lactation is more developed than in the lower. The process of gestation is also more developed. The attachment between the foetus and the uterus is closer. The nutrition of the foetus is more direct. The area of attachment is called the placenta and the higher orders of mammals, in which it is larger and more complex, are called the placentia. As the at¬ tachment becomes still more complex, the placentia are divided into the non-deciduate, in which the attach¬ ment is less complex and the response of the uterus to the needs of the foetus less immediate, and the de- ciduate, in which the attachment is more complex and is detached from the uterus after birth. The young of the deciduate placentia are all born quite feeble