Archive image from page 32 of The development of the frog's. The development of the frog's egg; an introduction to experimental embryology . developmentoffro00morg Year: 1897 Ch. II] POLAR BODIES AXD FERTILIZATION 17 produced by the filling and emptying of the lungs, and by the movements of the heart. Swammerdam's account in 1737 describes the passage of the egg from the ovaries to the oviducts by way of the coelomic space. Spallanzani in 1785 observed that the females of Bufo igneus, isolated before union with the male, could still la}' their eggs. One of the tree-frogs has its eggs in the u
Archive image from page 32 of The development of the frog's. The development of the frog's egg; an introduction to experimental embryology . developmentoffro00morg Year: 1897 Ch. II] POLAR BODIES AXD FERTILIZATION 17 produced by the filling and emptying of the lungs, and by the movements of the heart. Swammerdam's account in 1737 describes the passage of the egg from the ovaries to the oviducts by way of the coelomic space. Spallanzani in 1785 observed that the females of Bufo igneus, isolated before union with the male, could still la}' their eggs. One of the tree-frogs has its eggs in the uterus before it unites with the male. On the other hand, Spallanzani stated that females of the stinking toad if isolated while the eggs are still in the ovaries will retain their eggs, but if separated after having paired will then deposit their eggs. According to the evidence of several authors, Rana temporaria when isolated will, in certain cases at least, set free its eggs. It has been suggested that the embrace of the male is me- chanically necessary in order that the eggs may pass from the ovary into the oviducts, but this is certainl}'not „ '' ~ always the case, and if not necessary in one form , is probably not necessary •? in others. The sexual excitement set up by the tight embrace of the male may however be neces- sary in some species for the successful perform- ance of egg-laying. The \ eggs pass one by one n, down the length of the oviducts, ultimately to Fig. lO.—Egg iu jelly. (Aiter Schultze.) reacli the lower portion of the tube, the so-called uterus, A'here the eggs accumulate. If a frog is killed at the height of the breeding season, free eggs are often found in the body-cavity, and a series of eggs passing individually down the ovarian tubes, as well as an accumulation of eggs in the uteri. In their passage through the oviducts the eggs undergo certain internal changes and re- ceive also their egg-coats. In the tubes of the oviducts the nu- clear spind
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