246 BEATRICE WHITESIDE 
Stage VI (figs. 8, 15, and 19) 
The animal representing this stage was going through meta- 
morphosis. It was 15 mm. long and possessed well-developed 
anterior and posterior extremities. The tail was somewhat 
reabsorbed. 
The foramen endolymphaticum now lies still farther forward 
in relation to the brain. It is situated lateral to the lobi optici, 
in which position it is also to be found in the adult frog. 
In the posterior part of the saccus endolymphaticus a new 
communication appears between the two sacci. It is formed by 
the processus ascendens posterior, which, in the region of the 
cerebellum, runs over the brain and connects the saccus of the 
right side with that of the left (fig. 15, pr.asc.post.). 
The most striking difference between this stage and the pre- 
ceding one is the appearance of the calcareous sacs on the spinal 
ganglia. These structures are formed in the following manner: 
The posterior stem of the saccus, which runs backward inside 
of the vertebral canal, sends forth processes which extend through 
all the intervertebral foramina and as far as the spinal ganglia. 
The number and state of development of these transverse proc- 
esses vary in the different larvae examined at this stage. Some 
specimens have many processes, others very few. The condi- 
tion illustrated in figure 15 can frequently be observed. Here 
all the processes (y) have appeared, although in different degrees 
of development. Some of the sacs cover the entire ganglion, 
others only its proximal part. The most cranial processes, 
however, always appear first. 
The processus ventralis has now completed its growth and 
extends over the lateral and posterior surfaces of the hypophysis 
(figs. 19 and 8). Behind the hypophysis it runs underneath the 
brain until it joins the processus of the opposite side in the mid- 
ventral line. In this way a connection between the two sacci - 
endolymphatici takes place beneath the brain as well as above it. 
The division of the saccus into small tubuli has progressed 
further, and the whole organ now consists of many such structures. 
This continuous division was observed in a general way by Coggi 
