248 BEATRICE WHITESIDE 
(90), who examined older larvae and adult frogs. He writes 
as follows: 
Nei girini di rana le varie cavita che formano il sacco endolinfatico 
sono molto meno numerose e meno suddivisi che non aceada nelle rane 
adulte, ove la suddivisione va tant’ oltra gino a formare gli otricelli 
microscopici che ho descritto. 
Stage VII (figs. 9, 10, and 16) 
This stage is based on a young frog which had just completed 
metamorphosis. 
Compared with stage VI, the only change in the appearance 
of the saccus endolymphaticus is the increased size of the 
caleareous sacs. These structures have now assumed their 
definitive form. With this step the development of the saccus 
endolymphaticus is finished. The organ now has the following 
expansion. 
Soon after the ductus endolymphaticus enters the cranial 
cavity through the foramen endolymphaticum, it expands into 
a large thin-walled sac, which lies in the interdural space, lateral 
and dorsal to the brain and the spinal cord. From the foramen 
endolymphaticum a part of the saccus runs cranially, lateral to 
the lobi optici and the diencephalon, and reaches the anterior 
lateral surface of the hemispheres. ‘Two processes start from this 
main section of the pars cranialis anterior. From its anterior end 
the processus ascendens anterior runs dorsally until it meets 
the corresponding process of the other side. In the region of 
the foramen endolymphaticum the processus ventralis runs ven- 
trally and surrounds the ganglion prooticum commune and the 
lateral surface of the hypophysis. Behind the latter organ it 
proceeds farther in a median direction until a union of the proc- 
esses of the two sides takes place. 
The pars posterior starts from the foramen endolymphaticum 
and runs caudally, lateral to the lobi optici and the cerebellum, 
and dorsal to the plexus choroideus of the fourth ventricle. 
Above the cerebellum the narrow processus ascendens posterior 
connects the two saecci. At the end of the fourth ventricle the 
pars posterior widens in a median direction and the sacci of the 
