94 



PRESH-WATEE AQTJAEIA. 



The metamorplioses of the frog (Fig. 78) and toad are most 

 interesting, and can easily be observed by the help of the 

 aqnarium. The spawn of either the frog or the toad may be 

 obtained during the early part of the year, from almost every 

 ditch and pond. In the South of England it is sometimes 

 found in January, and frequently in February. The speed 

 of the development of the tadpole from the egg depends 



Fig. 78. Metamorphoses of the Frog, showing the growth of the Embryo, 

 from the Egg to the Four-legged Tadpole. 



greatly upon light and heat. The spawn of frogs may be 

 readily distinguished from that of toads, for the former is 

 found in shapeless masses, while the latter is deposited in 

 strings of two rows each, placed alternately and regularly. 

 These strings vary greatly in length. Eggs of toads are also 

 smaller and rather darker than those of frogs. The spawn 

 of either, when first laid, consists of small globular bodies 

 surrounded by a glutinous envelope (Fig. 78, a), into which 

 a large, quantity of water is quickly absorbed (&). The whole 

 then has somewhat the appearance of small shot embedded 

 in jelly. The development of the embryo can be easily seen 

 through its almost transparent covering, and the following 



