SPAWNING OF FROGS 



283 



species of frogs reach 

 maturity in different 

 periods of time. At 

 maturity, the female 

 frog lays fifty or a 

 hundred eggs, ova, in 

 the water. Each ovum 

 consists of a tiny ,cell 

 surrounded by yolk or 

 food which is covered 

 with a gelatinous 

 coating. The adult 

 male frog discharges 

 sperms into the w^ater. 

 These sperms are mo- 

 tile, swimming by 

 means of tinv tails. 

 If a sperm comes in 

 contact with an egg, 



it penetrates the egg The cow, placid in disposition, is easily distinguished from 

 , , , the excitable and frequently dangerous bull. 



membrane, and the 



nuclei of the egg and sperm unite in the fertilization process. If the 

 eggs are not fertilized, they soon die and disintegrate. If sperms 

 do not reach eggs, they, too, are wasted. The fertilization of 

 the frog's eggs is external to the body and takes place in the 

 water. Tliis differs from the plant where fertilization was in- 

 ternal, taking place in the ovary of. the i)istil. After fertilization, 

 the gelatinous sheaths of the frog's eggs absorb water and swell. 

 This mass of foamy material insures some degree of protection 

 against enemies. Fish or other frogs cannot readily swallow this 

 huge mass of gelatinous eggs. 



Fish spawn in a way very similar to frogs. They usually go to 

 quiet, shallow waters for spawning, although a few species of 



