ZOOLOGICAL LB D WW \ MCAL ASSOCIATION. 1 1 



ih. puiiii luges it to seek tor shallow or stagnant water, wherein at 

 the proper season to deposit the spawn ; rarely in running water is the 

 spawn found, and never in deep places, for, if placed in water even 

 few feet deep, it sinks to the bottom and rots away undeveloped ; shaded 

 places are generally selected, such as pools and ditches, into which the 

 sunlight does not shine, for, if subject to a strong sunlight and fa 

 there is danger that all the water in the pool would be too quickly eva- 

 porated, and the brood destroyed before being fitted to pass from an 

 aquatic to a terrestrial existence. At the very commencement of life 

 the tadpole in the natural state is supplied with nourishment in the 

 jelly-like material of the spawn, a substance which, according to Brande,* 

 is intermediate between albumen and gelatine, and which Higginbottom 

 shows to be of great consequence in the early growth of the creature. 

 Somewhat later they feed upon both vegetable and animal matter. In 

 the month of May those taken from their native pools have already the 

 lungs beginning to appear, and at this period, if watched in the natural 

 state, it will be seen that they swim to the margin of the shallow water 

 in which they live, and there lie. In June the limbs begin generally 

 to appear, and as soon as the anterior pair have become free, the little 

 animals make use of them to mount upon the duckweed, so constantly 

 growing where they exist, or clambering up the shelving margins of 

 their pools, and, for a time practising aerial respiration, they descend 

 again into the water ; at this period the branchiae still exist, and the oper- 

 cular coverings are not yet closed. In August and September, the 

 development being completed, they, as perfect frogs, leave the waters. 

 Indeed, it is rare in September, except in the cases I have seen in deep 

 quarry-holes, in pools in rocks, to find any tadpoles remaining, and, so 

 far as I am aware, they never in this country remain, as Edwards says 

 they do in France, the whole winter in the tadpole state, becoming frogs 

 the following spring. 



How different are the circumstances in which the tadpoles are placed 

 in Experiments 6 and 7 ; independently of the variety as to light 

 and food, all were in water very deep as compared with their native pools. 

 The vertical side of a glass vessel differs altogether from the gently 

 sloping bank, and offers no facility for the tadpole to rest near the sur- 

 face when the aerial respiration is about to commence, and when proxi- 



• Philosophical Transactions, 1810. 



