AMPHIBIANS—GOIN 429 
the tropical, wormlike caecilians, lay large-yolked eggs on land, and 
suggested that this may also have been true of the earliest amphibians. 
More recently, Romer (1957), in discussing the adaptive advantages 
of the terrestrial egg, hypothesized that the terrestrial egg preceded 
the terrestrial adult. 
Several other aspects of amphibian life history have recently been 
explored by various workers. Lutz (1947) summarized the trend 
toward direct development in frogs, and a year later (Lutz, 1948) 
again discussed developmental variation, this time with particular 
emphasis on the amount of yolk in the egg. Orton (1949, 1951) has 
particularly interested herself in the modifications in the larval 
stages as correlated with direct development in frogs. More recently 
Jameson (1955) produced an excellent summary of modifications in 
mating behavior of the anurans. 
Let me now summarize briefly the life-history modifications shown 
by the various living families of amphibians. 
Caecilidae —Among the caecilians, internal fertilization is the rule. 
In the male, the cloaca (the common chamber into which the digestive 
and reproductive tracts empty) can be everted and serves as a copu- 
latory structure when the cloacas of the two sexes are brought to- 
gether. We find both aquatic and terrestrial caecilians and their life 
histories reflect these differences. In /chthyophis, a native of Ceylon, 
breeding takes place in spring. A burrow is prepared by the female 
in moist ground close to running water. She coils her body about the 
20 or more relatively large-yolked eggs and guards them zealously 
during development, protecting them from predatory snakes and 
lizards. The eggs swell gradually until they are about double their 
original size. When ready to hatch, the embryo weighs approxi- 
mately four times as much as did the original egg. External gills are 
present at first, but these are lost soon after hatching. The larvae, 
which are aquatic, metamorphose into burrowing, limbless adults that 
would drown if kept under water. The genus 2Ainatrema of northern 
South America likewise has eggs that hatch out into aquatic larvae 
with external gills. 
On the other hand, Gymnophis and Geotrypetes retain the eggs in 
the oviducts and give birth to young which are replicas of the adults. 
The wall of the oviduct is provided with compound oil glands and the 
larvae subsist by literally eating the tissue of the wall with its in- 
cluded oil droplets. 
Hynobtidae——The hynobiids, primitive salamanders of the Old 
World, practice external fertilization, and the females deposit the 
eggs inegg cases. Batrachuperus karlschmidti, a common salamander 
of the small mountain streams of western China, attaches its egg 
cases in the stream bed proper, under or on the sides of large stones 
