480 ZOOLOGY. 



the adult, terrestrial form, sometimes being about a third of 

 a metre (12 inches) in length, the adult being twenty centim- 

 etres (8 inches) long, forming an example of what occurs 

 in the Amphibians and also certain insects, of the excess in 

 size and bulk of the larva over the more condensed adult 

 form. This law is also strikingly observed in the Pseudes 

 (Fig. 437). This fact of prematuritive, accelerated, vegetative 

 development of the larva over the adult is an epitome of what 

 has happened in the life of this and other classes of animals. 



The fossil, earliest 

 representatives of the 

 Amphibians, as we 

 shall see farther on, 

 were enormous, mon- 

 strous, larval, prem- 

 ature forms corn- 

 Fig. 435. Siredon or larval Salamander. From pared With their de- 



Tenney's zoology. scendants. The same 



law holds good in certain groups of Crustacea (trilobites), 

 insects, fishes, reptiles and mammals. 



The axolotl or siredon abounds in the lakes of the Eocky 

 Mountain plateau from Montana to Mexico, from an altitude 

 of 4000 to 8000 or 9000 feet ; the Mexican axolotl being of 

 a different species, though closely allied to that of Colorado, 

 Utah and Wyoming. The Mexicans use the animal as food. 

 Late in the summer the siredons at Como Lake, Wyoming, 

 where we have observed them, transform in large numbers 

 into the adult stage, leaving the water and hiding under 

 sticks, etc., on land. Still larger numbers remain in the 

 lake, and breed there, as I have received the eggs from Mr. 

 William Carlin, of Como. Thousands of the fully-grown 

 siredons are washed ashore in the spring when the ice melts. 

 They do not appear at the surface of the lake until the last 

 of June, and disappear out of sight early in September. 

 The eggs are laid in musses, and are 2 millimetres in diameter. 

 Mr. F. F. Hubbell has observed in Como Lake, July 23d, 

 young siredons four to six centimetres (1- 2-J inches) in 

 length, and September 3d specimens eight centimetres (3 

 inches) long. In Utah, Mr. J. L. Barfoot raised in 1875 



