DEVELOPMENT OF THE SACCUS ENDOLYMPHATICUS 235 
which I shall quote in the course of my paper, while all that 
Villy writes on the subject is the following paragraph: 
Until the semicircular canals are formed, little is to be noticed regard- 
ing the ductus endolymphaticus except a general growth in size, accom- 
panied by a movement towards the brain, so that it comes to lie in 
close contact with this organ. As the distal part comes close to the 
brain, it begins to expand and its duct narrows; at the same time the 
upper lip of the duct elongates, so as to carry the vestibular opening 
downwards. The distal enlarged part grows, and, as the tadpole 
loses its tail, assumes the permanent proportions, becoming at the same 
time thin walled and vascular, while the organs of the two sides meet 
both above and below the brain. Whether actual communication is 
set up is difficult to determine by means of sections alone. The growth 
of cartilage between the expanded end of the organ and the rest of the 
vestibule does not take place until late and even then a foramen is 
left, through which the duct passes from the vestibule to the skull- 
cavity. It would seem to have some function of importance in the 
adult, as it steadily increases in size during the growth of the tadpole 
.and it is after the tadpole stage is passed that this increase in size be- 
comes most rapid and the blood supply most copious. 
DESCRIPTION OF DEVELOPMENT 
1. Material and methods of preparation 
The material consisted of larvae of Rana temporaria Linné. 
The investigation was conducted chiefly by means of series of 
sections, of which thirty were made, six representing the first 
stage and four each of the following stages. The larvae were 
first narcotized with ether and the gut extracted. ‘The larvae 
were then fixed in sublimate (twenty-four hours). As I wished 
to pay special attention to the lime contents of the saccus, it was 
not possible to decalcify. This rendered section cutting very 
difficult. In order to make the preparations more fit for section- 
ing, they were left a long time in the various media. ‘They re- 
mained in 70 per cent alcohol for twenty-four hours, in 95 per 
cent for thirty-six hours, and in 100 per cent for twelve hours. 
Thereupon a little cedar oil was added to the 100 per cent alcohol, 
~ and the quantity of oil was gradually increased. After four hours, 
the larvae were placed in pure cedar oil, in which they remained 
four weeks. At the end of this time they were brought once 
