No. 405.] DEVELOPMENT AMONG ANURA. 697 
The egg contains an unusual amount of yolk, and is not 
pigmented ; the segmentation was formerly thought to be 
meroblastic, but it has recently been described as similar to 
that of Bombinator. The embryo is said to be ciliated even 
on the head. Certain peculiarities in the development of the 
alimentary canal have been recorded. The cavity is at first 
wide, and in the foregut and hindgut it remains in this condi- 
tion, the anterior end having the widest lumen ; in the middle 
region the ventral yolk-mass is raised in a ridge, toward the 
dorsal wall, so that the midgut is, for a time, nearly or en- 
tirely barricaded. An early description seems to indicate that 
the cesophagus is at one time closed by yolk-cells, as in the 
frog. The liver is said to develop independently, and shortly 
to acquire an opening into the alimentary canal. It is also 
said that the vitelline veins are at first not connected with the 
liver, but pass into it later as the portal vein. The lungs arise 
as solid masses of cells in the cesophageal region, and subse- 
quently become hollow. An adhesive gland is not mentioned. 
Before the gills develop, four gill-slits break through; the 
external gills are then represented by a single pair, on the 
third visceral arch; they grow to an unusual length during 
the life in the egg, and are branched eight or ten times. 
These delicate plumes are very highly vascular and therefore 
bright red, and are easily seen through the egg-membrane. 
When the tadpoles are about ready to leave the egg, the 
hatching may be hastened or retarded within the limits of two 
or three days, by bringing the eggs into water a little before 
or after the normal time. Tadpoles that were put into water 
long before the usual time, for example when the external gills 
were fully. developed, fruitlessly turned within the egg-mem- 
brane, and finally died.! On the other hand, Agassiz tried 
without success the converse experiment of raising the newly 
hatched young in air. _ 
Some interesting facts have been discovered in connection 
! The experiment of first cutting away the egg-membrane and then leaving the 
tadpoles in water was apparently not tried. Compare experiments on the embryos 
of the viviparous Salamandra atra. Those taken from the uterus, if tended with 
Breat care, cast off their gills in water and develop a new set. Chauvin (77). 
