DEVELOPMENT OF THE SACCUS ENDOLYMPHATICUS 261 
first to examine the saccus endolymphaticus in this class, writes 
that in Coluber natrix the saccus is represented by a small vesicle 
lying directly under the suture between the parietale and occi- 
pitale. The sacci of the two sides lie close to one another, but 
do not join. Hasse investigated Anguis fragilis, Lacerta viridis, 
Chelonia midas, Testudo graeca, and Crocodilus. In all of 
these animals he found the expansion of the saccus similar to 
that in Coluber. 
The only reptiles whose saccus endolymphaticus does not 
conform to the above-given description are the Ascalabotae. 
According to Wiedersheim’s (’76) investigations on Phyllodacty- 
lus, the saccus does not only run upwards to the roof of the brain, 
but also extends backwards. It leaves the cranial cavity through 
a small aperture in the parietale, passes back between the muscles 
of the neck, and ends in the region of the pectoral girdle with 
a large closed sac. All the parts of the saccus are filled with 
calcareous matter, in the adult as well as in the embryo. In 
Phyllodactylus the two sacci do not join; in Ascalabotes, however, 
they coalesce a little behind the posterior part of the parietal 
suture. They separate again when leaving the cranial cavity. 
Many species of Platydactylus have a similar extension of the 
saccus. Gray (’08) did not find this formation in Tarentola 
mauretanica. He thinks that perhaps it was destroyed by the 
manner of preparation. 
Hasse writes that the structure of the recessus labyrinthi in 
Aves is very similar to that in the Reptilia. He was not able to 
state whether lime crystals are present at any period of develop- 
ment. According to Wiedersheim (’06), the saccus is filled with 
lime in the embryo stage. 
The Mammalia show a slight deviation in the anatomical 
structure of the ductus endolymphaticus. In these animals the 
duct arises from the labyrinth with two branches, one from the 
lower median side of the utriculus, the other from the upper 
median part of the sacculus. The two branches soon join and 
the ductus leads upward at the median side of the utriculus, as 
far as the foramen endolymphaticum. Here it runs into the 
cranial cavity and ends inside the dura mater with a small dila- 
