534 



Experiment 3rd. Some spawn was placed 8 inches below the 

 surface of the water ; but none of the ova passed through the branchial 

 state. 



Experiment 4th. A quantity of spawn was placed on rock work 

 near the surface of the water. Nearly all the ova passed satisfac- 

 torily through the branchial state to the formation of tadpoles ; each 

 of the experiments was made at the same time and at the same tem- 

 perature. 



Experiment 5th. A quantity of spawn was put into two round 

 shallow dishes, each containing two pints of water, which were placed 

 on the stand of the aquarium at the same time as in the former experi- 

 ments; nearly all did well; and during the full branchial or fish-like 

 state, great numbers of the embryos had placed themselves close to 

 the margin of the water, forming a dark circle, with their branchiae 

 nearly exposed to the atmospheric air. They do not appear to feed 

 during this period on the jelly their first food ; atmospheric respira- 

 tion seems more needful than food for their existence for several 

 days during their full branchial state*. 



There are two distinct metamorphoses from the ovum to the full 

 development of the frog : the first from the branchial or fish- like state 

 to that of the tadpole ; the second from the tadpole to that of a frog, 

 the first requiring for its existence a close approximation to the at- 

 mospheric air, the second requiring full atmospheric respiration, to 

 which I shall hereafter refer. 



The branchial state continues about nine days, from the first bud- 

 dings of the branchiae to their absorption. About the seventh day 

 the branchiae are absorbed on the right side, indeed so quickly that 

 I have observed that scores have lost them during one night, whilst 

 the branchiae on the left side have apparently been perfect ; but these 

 in their turn become absorbed during the next day ; the respiration 

 of this newly formed tadpole now depends on the internal gills and 



* The ova of the toad appear to be less tenacious of life than those of the frog. 

 I have observed, when they are placed 4 or 5 inches below the surface of the water, 

 they all die ; but they live when the long jelly lines in which the ova are enclosed 

 are floated on weeds, or on a network of sticks on the surface of the water. In 

 my note-book on the tadpole of the toad^in 1849, 1 found that after the gelatinous 

 lines began to break up on the surface of the water, and the ova to separate from 

 them, a number of the eggs undergoing the metamorphosis adhered to the sticks 

 and weed, but those falling to the bottom of the vessel perished. 



