CHAPTER SIXTEEN. 

 THE FAMILY OF THE FROGS 



1. The Family Tree. A great many of our examples in 

 the earlier part of this book have been taken from the 

 plants and the lower animals, the invertebrates. The 

 frogs, along with the fishes, birds, and men, are vertebrates. 

 The class of vertebrates to which frogs belong is not a 

 very large or important one, but it is one of the very most 

 interesting because of its method of reproduction and 

 development. In the family are frogs and toads, tailless 

 forms, including many kinds of tree toads; and a number 

 of slimy animals with tails, somewhat like lizards, that 

 live in water or moist places. These latter are newts, 

 salamanders, sirens, "mud-dogs," and the like. 



The frogs and toads breathe in the air, and may live on 

 land, but they (the frogs, particularly) spend much of 

 their time in or near the water. Most of the family would 

 die if long out of water. 



2. Reproductive Habits of the Frog. The frogs have 

 two sexes. The mother lays large masses of eggs in the 

 water. The egg proper, which is about the size of medium 

 shot, is dark in color and is surrounded by a layer of clear 

 transparent gelatin which helps to hold the eggs together 

 in globular masses or in strings, depending on the species. 

 Frogs do not lay eggs in nests, or specially prepared 

 places; but the frogs and even the land toads go regularly 

 in early spring to the shallow margins of pools and 

 streams. The eggs are frequently attached by the gelatin 



