ZOOLOGY: E. P. ALUS 
241 
pointed out 3 that,when crystal penetration is properly corrected for, the curve 
of atomic number versus square root of frequency is almost a straight line, theii 
own values falling more nearly on a straight line than either those of Moseley 
or de Broglie. As a matter of fact it is manifest that the effective reflected 
ray for a crystal like calcite is along such a direction as to make the measured 
angle of reflection proportionately too large for the higher frequencies. In 
other words as the atomic number increases the measured frequency is pro- 
portionately greater than it should be. This possibly accounts for the fact 
that the curve in figure 3 of Blake and Duane's paper is convex downward 
toward the axis of atomic numbers. It would seem that a test of this reason- 
ing could be made by repeating the work of Blake and Duane using a crystal 
with a cubic lattice but one whose faces are as good as those of calcite (rock 
salt is notoriously bad), care being used of course to correct for crystal pene- 
tration, or to eliminate the effect of such penetration by using a very narrow 
incident beam and having the ionization chamber slit very wide (the arrange- 
ment shown in figure 1, first used by Duane and Hunt 4 ). 
1 Physic. Rev. Ithaca, 10, 1917, (624-637). 
2 Pro . Roy. Soc, (A), 89, 1914, (468). 
3 Physic. Rev. Ithaca, 10, 1917, (703). 
4 Ibid., August, 1915, p. 166. 
THE MYODOME AND TBI GEM I NO-FA CIA LIS CHAMBER OF 
FISHES AND THE CORRESPONDING CAVITIES IN 
HIGHER VERTEBRATES 
By Edward Phelps Allis, Jr. 
Palais Carnoles, Menton, France 
Communicated by E. L. Mark, June 20, 1918 
A functional myodome is found only in fishes, and even among them it is 
limited, in the specimens I have examined, to Amia and the non-siluroid 
Teleostei. 
The myodome is always separated from the cavum cerebrale cranii by either 
membrane (dura mater), cartilage or bone, and the separating wall is in part 
spinal and in part prespinal in position. A depression in the prespinal por- 
tion lodges the hypophysis, or both the hypophysis and saccus vasculosus, and 
this part of the wall never undergoes either chondrification or ossification, a 
more or less developed pituitary sac always projecting into the myodome. 
The myodome is found in its most complete form in the Teleostei, and there 
consists of dorsal and ventral compartments, which are usually separated from 
each other by membrane only, but that membrane, the horizontal myodomic 
membrane, is capable of either chondrification or ossification. The dorsal 
