. Comparative embryology of the vertebrates; with 2057 drawings and photos. grouped as 380 illus. Vertebrates -- Embryology; Comparative embryology. 222 FERTILIZATION lized, when these degenerative (cytolytic) conditions are initiated, fail to develop normally. If allowed to continue, cytolysis soon produces a condition in which development is impossible, and dissolution of the egg results. 3) Low Level of Respiration. While the egg is in this inhibited or arrested state awaiting the event of fertilization, respiration is carried on at a steady but low level. This respiratory level varies in d
. Comparative embryology of the vertebrates; with 2057 drawings and photos. grouped as 380 illus. Vertebrates -- Embryology; Comparative embryology. 222 FERTILIZATION lized, when these degenerative (cytolytic) conditions are initiated, fail to develop normally. If allowed to continue, cytolysis soon produces a condition in which development is impossible, and dissolution of the egg results. 3) Low Level of Respiration. While the egg is in this inhibited or arrested state awaiting the event of fertilization, respiration is carried on at a steady but low level. This respiratory level varies in different animal species (fig. 120). That this respiration rate may not be the direct cause of egg inhibition, is shown by the fact that the rate of respiration does not always increase imme- FEMALE NUCLEUS SPERM TAIL. Fig. 115. (A) Early fertilized egg in upper Fallopian tube of the bitch (dog). Observe the female nucleus before the first maturation division together with the sperm head and tail. Note that the sperm, as in other mammals, enters the nuclear pole of the egg. Observe further that the zona pellucida and the ooplasm are contiguous. (B) Section of the egg of the dog, taken from the upper part of the Fallopian tube. Observe the following features: (1) The sperm pronucleus is forming; (2) the egg nucleus has now entered the meta^hase of the first maturation division; (3) the ooplasm of the egg has shrunk away from the zona pellucida and a space is present between the egg and the zona. This space is the perivitelline space, containing an ooplasmic exudate. (C) Sec- tion of the egg in the Fallopian tube of the bitch, showing the formation of the first polar body. diately following fertilization in all species (fig. 120). (Consult Brachet, J., '50, p. 105.) Among the vertebrates, the low rate of oxygen consumption of the unfertilized egg has been shown to continue for some time after fertili- zation in the toad and frog egg and also in the egg of the teleost fish, Fundulu
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