ix THE SKIN 187 



described (see Chapter II). The males of certain species 

 assume at this time a blue coloration which appears mainly 

 on the ventral side of the body. In Rana arvalis (/?. oxy- 

 rrhinus) it has been described by Steenstrup and by Siebold. 

 In Rana fuscci Falio described a blue coloration appearing 

 on the throat during the breeding period. Leydig found 

 that this color disappeared soon after the animal was taken 

 from the water. Both Leydig and Haller, who studied the 

 same phenomenon in Ra/ia temporaria, regard the blue as 

 an interference color produced by minute granules in the 

 skin. It is probable that the appearance of the blue color 

 is associated with the absorption of water. Frogs which 

 have lost the blue color when kept in the air soon regain it 

 when placed in the water again. After the breeding period 

 is over, the blue color quickly disappears. A reddish brown 

 color during the breeding season has been described by 

 Leydig in the female of Ranafusca, and Smith has observed 

 a blue coloration of the throat which he regards as charac- 

 teristic of the female of that species at this time. 



The skin of the male of Ranafusca in the breeding sea- 

 son becomes swollen and may hang down at the sides, 

 assuming what Leydig designates a " quammig-quappiges 

 Ansehen." The stratum compactum of the corium becomes 

 more or less gelatinous and the subcutaneous lymph spaces 

 become filled with a material resembling the vitreous humor 

 of the eye. 



With the exception of the swollen first finger of the male 

 and the dermal papillae of the female there is no evidence 

 as to what functional significance the above characters pos- 

 sess, if they possess any. They may be the incidental prod- 

 ucts of the important constitutional changes which take 

 place during the breeding period, without being of any 

 direct value to the organism. 



