ence, although most of them are still restricted to damp situations. Those of 

 the genus Amhystoma migrate to the ponds for egg-laying, but the Plethodons 

 are completely emancipated and pass even their larval stages on land. The 

 tree salamander, Aneides luguhr^s, a native of California, is our only truly ar' 

 boreal salamander, with habits of climbing trees and making homes in their 

 cavities. 



Details of reproduction vary in different forms. A few foreign species 

 bring forth living young. Most of the Amhystomidae lay masses of pigmented 

 eggs in water, each egg having one or more gelatinous envelopes and the whole 

 bunch having a common envelope. The egg-laying usually occurs in the spring, 

 but the marbled salamander, Amhystoma opacum, lays its eggs in the autumn, 

 under the moss and leaves of areas which will be the floors of temporary ponds 

 in the spring. Hatching is delayed until favorable conditions arrive. Many of 

 the Plethodontidae lay at the edge of the water or on land, usually under moss 

 or rocks in damp locations. Their eggs are usually without pigment and are 

 suspended individually by slender, gelatinous stalks. The tree salamander, 

 Aneides luguhris, often lays its eggs in the cavity of the tree it uses for a re' 

 treat. Members of this family and some of the others have been reported as 

 brooding, or at least staying by, their developing eggs. It is possible that by 

 doing so they aid in maintaining the proper conditions of moisture, but it seems 

 probable in many cases that the eggs are deposited in the usual retreat of each 

 female, which it continues to use after the eggs have been laid. The latter idea 

 seems a likely explanation of reports of brooding by such an aquatic form as 

 T^lecturus, unless it may possibly stay by its eggs to protect them from destruc- 

 tion by other aquatic animals. The common newt deposits its eggs separately, 

 usually wrapping each in the leaf of some water plant. Triturns torosus, the 

 California newt, lays its eggs in small bunches much like those of the Amhy- 

 stomidae. The giant salamanders, Amphiuma, Cry ptohranchns and 7\[ecturiis, 

 deposit unpigmented eggs in water. The first two lay numbers of eggs con- 

 nected by slender strings of jelly. J\[ecturus suspends its eggs separately from 

 the under sides of submerged rocks or logs. One of the Amhystomidae, Am- 

 hystoma tigrmum, the tiger salamander, may under certain conditions remain 

 in the larval stage and reproduce without losing its gills and transforming into 

 the typical adult form. This peculiar stage is called the axylotl, the name by 

 which it is known (and eaten) by the natives of Mexico. The mudpuppies (of 

 the family 7S(ecturidae) are forms in which this condition of arrested develop- 

 ment in everything but reproduction has become firmly established. A few of 

 the Plethodontidae also retain gills and other larval characteristics throughout 

 life. 



For purposes of illustration it seems best to give a more extended account 

 of the reproduction and development of one of the most commonly studied 

 salamanders, Amhystoma maculatum. Because of the great variation of breed' 



308 



