256 BEATRICE WHITESIDE 
Si l’on ouvre de bas en haut le labyrinthe d’une Grenouille, on est 
surpris de trouver le petit sac plein d’une masse crétacée presque entiére- 
ment de méme nature que les singuliers corps laiteux ou crayeux qul 
garnissent les trous intervertébraux destinés au passage de nerfs rachi- 
diénes. Les deux masses quand on les examine au microscope, parais- 
sent consister en plusieurs millions de cristaux de carbonate calcaire, 
arrondis et ovalaires, dont les plus gros ont environ un centiéme de 
ligne de long, et dont la forme est celle d’un prisme a six pans terminé 
par des sommets a six faces. 
The entire saccus endolymphaticus may, as Lenhossék suggests 
in regard to the calcareous sacs, be compared to a tubular gland 
without an outlet. The contents of the saccus would then repre- 
sent the secretion of the glandular cells. In any case, we must 
not forget that these cells are derived from the labyrinth, whose 
epithelium has the same ability to produce lime. 
Summary 
The first fact to be noticed in the course of development of the 
saccus endolymphaticus is the comparatively late differentiation 
of this organ. Ina larva of 4mm. length, whose auditory organ 
is in an advanced state of development, the saccus endolymphati- 
cus is present only as a shght expansion of the distal end of the 
ductus. At a time when all the morphological parts of the 
labyrinth are recognizable, this structure is still a small sac, 
adhering to the roof of the fourth ventricle. According to 
Norris (92) and Fleissig (08), the first indication of the saccus 
appears also very late in Amblystoma and Ascalabotes. 
The further development of the saccus proceeds very slowly. 
First an increase in length takes place in a craniocaudal direction, 
until the saccus reaches from the hemispheres into the region of 
the seventh vertebra, the saccus of one side remaining separated, 
however, from that of the opposite side. Next there develops, 
in a larva 12 mm. long, the processus ascendens anterior. ‘This 
is very soon followed by the joining of the partes spinales and 
the first indication of the processus ventralis. The processus 
ascendens posterior appears at the beginning of the metamor- 
phosis. About this time the calcareous sacs also are to be seen. 
