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THE TRANSITION TO LAND 



of sperms (spermatophores) on leaves or other objects in the bottom of 

 the pond. The female comes along behind him and picks them up with 

 the lips of her cloaca. The sperms are stored in special organs in her 

 body. Later when she lays eggs some of the sperms are released and 

 fertilize these eggs as they pass through her cloaca, although by this 

 time the male may be far away. 



Amphibians that lose their tails as adults are either frogs or toads. 

 The toad lives more as a land animal than the frog and has developed a 

 dry, warty skin. It is sometimes thought that a person may get warts 

 by handling a toad because of their presence on the toad's skin, but there 

 is not the slightest foundation for such belief. The eggs of toads may be 

 distinguished from those of frogs when seen in the water. Toad eggs 

 are laid in a long string and look somewhat like beads on a string, while 

 frog eggs are laid in a gelatinous mass. The frogs have been discussed 

 in Chapters 22-24 as typical chordate animals. 



Class — Reptilia 



The transition from water to land habitat, started by the amphibians, 

 is completed by the reptiles. This has been accomplished by the de- 

 velopment of a copulatory organ in the male and the development of an 

 egg that can hatch on the land. Also many changes in other body 

 organs have come about as an adaptation to life on the land. Like some 

 amphibians, there are reptiles, such as turtles and crocodiles, that spend 



Fig. 26.4. The developing embryo of a reptile or bird. Note the large yolk sac 

 which supplies food to the developing embryo and the allantois which takes care of 



respiration. 



