530 METAMORPHOSIS IN AMPHIBIANS 



WolterstorfP^" observed that the coloration continued to develop in 

 urodelan larva whose metamorphosis had been checked; he men- 

 tioned that in this phenomenon we seem to deal with a noteworthy 

 case of organic correlation. He probably thought, however, — 

 erroneously as will be shown later on — that the development of the 

 skin pigmentation is conditioned by the development of the sex or- 

 gans, a correlation existing between these two organs. Later on 

 Kammerer^^ observed a larva of Salamandra maculosa which had 

 developed the skin pattern of the adult a year and a half before meta- 

 morphosis took place. Similar phenomena have been observed also 

 among the larvae of Salientia. Dickerson,!^ for instance, in a de- 

 scription of the metamorphosis of Rana clamitans, says: "The varia- 

 tion in the size, color, and markings of the changing tadpoles is very 

 great. Most curious is the fact that some tadpoles show the lateral 

 folds and the coloring of the adult male or female long before the 

 change is completed, while others take on the frog form entire before 

 the lateral folds are well developed or before the sexual coloring is 

 evident." 



The following experiments show that the development of the skin 

 coloration cannot be prevented by the absence of iodine from the 

 food, nor can it be enforced by the direct application of iodine; con- 

 sequently it is independent from metamorphosis and may take place 

 either before or after metamorphosis. 



Four series of larvae of Amby stoma opacum, all hatched from eggs of 

 one female, were kept at approximately 25°C.; two series (A and E, 

 1916) were fed earthworms, the other two {B and F, 1916) were fed 

 calf's thymus. In Series A and E the gray network of the adult com- 

 menced to develop as soon as the animals had metamorphosed (Figs. 



Figs. 1 to 4. Development of the adult coloration of the skin in worm-fed 

 and thymus-fed animals of Ambystoma opacum. In worm-fed animals the gray 

 network develops after metamorphosis (Figs. 1 to 3), in thymus-fed animals, the 

 metamorphosis of which is retarded, it develops before metamorphosis (Fig. 4). 

 Photographed from water color paintings made from the living specimens. Nat- 

 ural size. 



^^ Wolterstorff, W., Zool. Garten, 1896, xxxvii, 327. 



^^ Kammerer, P., Arch. Entwcklngsmechn. Organ., 1904, xvii, 165. 



12 Dickerson, M. C, The frog book, New York, 1907, 205. 



