244 BEATRICE WHITESIDE 
upwards and inwards. In the middorsal line the ascending 
processes join and unite with the paraphysis: This connection 
between the two sacci, called by Gaupp the processus ascendens 
anterior, has now attained its definitive form. 
The pars posterior of the main stem of the saccus endolym- 
phaticus extends from the foramen endolymphaticum into the 
region of the seventh vertebra. ‘The saccus of the one side is 
still separated from that of the other. The lumen of the saccus 
decreases caudally. 
The lateral extension of the saccus endolymphaticus is illus- 
trated in figure 17. As mentioned above, it lies at the side of 
the hemispheres, the diencephalon and the lobi optici. It is 
narrow in the region of the hemispheres and the diencephalon; 
in the region of the lobi optici, however, it widens and fastens 
itself onto the dorsal side of the ganglion prooticum commune 
(fig. 6, g.pr.c.). In the adult frog this ganglion represents 
the union of the trigeminal and facial ganglia. At the stage 
described here the two components are still to be recognized, the 
facial ganglion (g.fsc.) lying dorsal to that of the trigeminus 
(g.trig.). 
In the larva taken to represent this stage of development, 
the anterior part of each saccus endolymphaticus is an undivided 
sac. The posterior part of each saccus is, however, divided into 
two tubuli directly behind the foramen endolymphaticum. 
These tubuli run as far as the posterior end of the fourth ven- 
tricle, where they join once more. The whole saccus is filled 
with lime. 
Stage V (figs. 7, 14, and 18) 
The sections on which the descriptions of stage V is based 
were made from a larva 15 mm. long, in which the anterior 
extremities had appeared. 
The first thing to be noticed is that the position of the foramen 
endolymphaticum has changed in its relation to the brain. This 
opening no longer lies beside the plexus of the fourth ventricle, 
but at the side of the cerebellum. The change in position is 
probably due to the fact that the cerebellum has expanded 
backwards in the course of its rather late development. 
