AMPHIBIANS—GOIN 431 
contain on the average about 16 eggs. ‘These eggs are, of course, 
fertilized as they pass down the oviduct. Since the female may de- 
posit over 200 eggs, it often takes a number of masses to complete a 
deposition. Typically, the incubation period ranges from 380 to 45 
days, and transformation, or metamorphosis, follows 2 to 4 months 
after hatching. 
A. opacum departs from this pattern to lay its eggs in the fall on 
land under old logs or other sheltering objects. The young, which 
hatch out on the advent of winter rains and make their way into the 
water, exhibit all the larval characteristics typical of other species of 
the genus. 
Salamandridae.—The typical salamanders have developed a diver- 
sity of life-history patterns. Fertilization is internal by means of 
spermatophores. In the common American newt, Diemictylus v. viri- 
descens, mating takes place in the spring. The eggs, numbering 
200 to 375, are laid singly and usually are fastened to some aquatic 
object, such as a leaf or the stem of a small plant in quiet waters. 
Rarely they may be attached to the surface of a stone. The eggs 
hatch in about 20 to 35 days and the larval period usually lasts until 
fall. 
On the other hand, some species of the Old World genus Sala- 
mandra exhibit modified life histories. Salamandra atra, for ex- 
ample, retains the eggs in the oviduct for the developmental period, 
and the young are born as fully metamorphosed individuals. In 
S. salamandra the developing individuals are retained in the oviduct 
for a time, but they may be born as late larvae, rather than as com- 
pletely metamorphosed individuals. If the larvae of these two 
species are dissected from the oviduct, they are found to have the long 
filamentous gills and rudimentary balancers that are characteristic of 
pond larvae. This shows that in Salamandra the retention of the 
developing young in the oviducts is a modification of the aquatic form 
of life history. 
Amphiumidae.—While details of the congo eel’s life history remain 
to be discovered, the broad picture is evident. Fertilization is ap- 
parently internal and the eggs are laid in long, rosarylike strings in 
shallow depressions on land beneath old logs or boards. These strings 
contain, In some cases, at least 150 eggs. The normally aquatic fe- 
male remains with the eggs and guards them during their develop- 
mental period. 
Plethodontidae—Members of this specialized family of salaman- 
ders also show some specialized life histories. Hence, not one but 
several accounts are needed to typify the breeding habits of this 
family. In all the species, fertilization is internal by means of 
spermatophores, but from this point on, there are modifications tend- 
536608—60——29 
