THE AQUARIUM, APRIL, 1896. 



39 



(Salama/tdra maculosa) of Germany, 

 who gives birth to living young ; the 

 Surinam toad of South America, which 

 hatches its spawn and develops the 

 tadpoles in little cells on its back ; and 

 one or two species of tropical tree-frogs, 

 who deposit their eggs among damp 

 foliage, where the young hatch from 

 the eggs as perfect little frogs. 



The season of spawning differs also 

 in the various species, ranging from the 

 first of March until the end of June, 

 in our climate. The spawn of the tail- 

 less batrachians is fertilized outside of 

 the body, and deposited against plants 

 or other objects in the water. Frog- 

 spawn remains together in a lump ; 

 toads deposit their spawn in strings ; 

 the different species of treefrogs in 

 sheets, small clusters, or each egg 

 single. 



The green or spring frog (Ratia 

 fontimdis, Le C.) being a good repre- 

 sentative of the North American frog, 

 and one most frequently met with near 

 springs or creeks, has been chosen by 

 us for our illustration of the develop- 

 ment of the entire order. 



In Fig. 1 we see a lump of spawn, 

 greatly reduced in size, as it appears in 

 the water after it has been deposited by 

 the frog. Such a lump, when first 

 spawned is about the size of a small hen 

 egg ; the individual eggs, a couple of 

 hundred in number, having the size of 

 small shot. As soon as these ai-e ex- 

 posed to the action of the light and the 

 water, each expands and the lump at- 

 tains a size that would fill a large sized 

 soup plate to the rim. Each individual 

 egg is covered with an adhesive, trans- 

 parent substance which tends to hold 

 the lump together, and forming a cover- 

 ing over the entire mass, protects this. 

 To the touch such spawn feels like a 

 mass of jelly. 



Fig. 2 shows the embryos' natural 

 size, in the eggs, just before hatching. 



Fig. 3 are larva? of the tadpoles, just 

 hatched. 



Figs. 4 and 5, tadpoles in various 

 stages of development. In Fig. 4 we 

 observe gills on both sides of the head, 

 as in a fish, the tadpole being jet-black 

 in color ; in Fig. 5, the gill on the 

 right has disappeared, only the one on 

 the left of the tadpole remains, and this 

 has changed into a tube leading into 

 the body ; tlie coloring of the body has 

 become an ashy gray speckled with 

 numerous irregular dark spots. This 

 stage completes the tadpole. It grows 

 as such on vegetable diet to the size 

 shown in Fig. 6, and passes the winter 

 on the bottom of i)onds or in creeks. 



Towards the spring, when the tem- 

 perature of the water is affected by the 

 rays of the sun, the hind legs begin to 

 form, budding out very small on the 

 basis of the tail, outside of the body, 

 while at the same time the fore legs are 

 forming below the skin, as shown in 

 Fig. 7. When the latter are complete 

 in shape they poke through the skin 

 and the animal appears like a salaman- 

 der, its color having also changed to a 

 grayish brown (see Fig. 8). While the 

 legs are still undergoing full develop- 

 ment the shape of the head undergoes 

 a change, the mouth being changed in 

 shape and size to fit it for a different 

 diet, which will hereafter consist of live 

 insects or other creatures ; the eyes, too, 

 are undergoing a change, and the 

 structure of the breathing apparatus is 

 changing from that of a fish to that of 

 a land animal; in short, the gills change 

 into lungs. While these radical changes 

 in the structure of the animal are going 

 on, the individual takes no nourish- 

 ment from outside, the material neces- 

 sary for the completion of its structure 



