. Text-book of embryology. Embryology. Pio. 251.—String of eggs of unknown Frog from the Gambia. Individual variations in the rate of development are indicated by the varying size of the yolk-plug. and its richness in yolk and there is no group of Vertebrates which offers anything like the same facilities for studying the influence of yolk upon the course of development. Further it will be only after greatly extended studies on different species that we shall be in a position to I have a really com- I prehensive idea of typical Anuran development. Many tropical species of Frogs and Toads are t
. Text-book of embryology. Embryology. Pio. 251.—String of eggs of unknown Frog from the Gambia. Individual variations in the rate of development are indicated by the varying size of the yolk-plug. and its richness in yolk and there is no group of Vertebrates which offers anything like the same facilities for studying the influence of yolk upon the course of development. Further it will be only after greatly extended studies on different species that we shall be in a position to I have a really com- I prehensive idea of typical Anuran development. Many tropical species of Frogs and Toads are to be obtained alive from animal dealers and in these it may be taken as a general rule that breeding takes place at the commence- ment of the rainy season, or in other words when environmental conditions become favourable after a prolonged period during which they have been unfavourable. By bear- ing this principle in mind such tropical amphibians may usually be induced to breed in captivity. Bles in his excellent account of the life-history of JCenopus (1905) describes a method which will be found to be of general use. The pair of animals were kept in a Budgett tropical aquarium consisting of a glass bell-jar 20 inches in diameter dipping into a galvanized iron water-tank heated by a small Bunsen burner and oxygenated by plants of Vallisneria. During summer the temperature of the water in the bell- jar was kept at about 25 ° C. The water was not changed. The frogs were fed daily with small earthworms or thin strips of raw calf's liver until they would eat no more. In December the tempera- ture was allowed to fall to 15°-16° during the day and as low as 5"-8° during the night. As the temperature rose with the onset of spring the frogs became more active, waking up out of the lethargic condition induced by the winter's cold. Breeding was induced by simulating the natural conditions of the rainy season. The temperature was raised to about 22° C. Each morning and eveni
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