Talk:Book - The Frog Its Reproduction and Development 2

The rate of development of the egg and embryo will depend upon the temperature at which they are kept. The approximate schedule of development at two different temperatures is given below.

Stage At 18

Fertilization

Gray crescent 1

Rotation li/^

Two cells 3V2

Four cells 4V2

Eight cells 5V^

Blastula 18

Gastrula 34

Yolk plug 42

Neural plate 50

Neural folds 62

Ciliary movement 67

Neural tube 72

Tail bud 84

= c.

At 25"

C.

hrs. . . .

hrs.

1/2-1

1

. 21/2 '

" 31/2 '

41/2 '

12

20

32

40

48

52

56

66

Stage Atl8°C. At25°C.

Muscular movement 96 hrs 76 hrs.

Heart beat 5 days 4 days

Gill circulation 6 " 5

Tail fin circulation 8 " 6V^

Internal gills, operculum 9 " IV2

Operculum complete 12 " 10

Metamorphosis 3 mos IVi mos.