556 
ZOOLOGY: C. STOCKARD 
composition. Cor allium and Tubipora, for example, are compact forms, 
with little organic matter; and they are lower in magnesia than the 
genera with horny, organic axes, such as appear at the end of the table. 
It is also noteworthy that the highest proportions of calcium phosphate 
are commonly found associated with high values for magnesia. 
1 Published by permission of the Director of the U. S. Geological Survey. 
AN EXPERIMENTAL ANALYSIS OF THE ORIGIN AND RELA- 
TIONSHIP OF BLOOD CORPUSCLES AND THE LINING 
CELLS OF VESSELS 
By Charles R. Stockard 
DEPARTMENT OF ANATOMY. CORNELL UNIVERSITY MEDICAL SCHOOL 
Presented to the Academy, September 29, 1915 
Studies on the origin and development of the cellular elements of the 
blood and the so-called endothelial cells which line the blood vessels in 
the normal embryo are peculiarly difficult on account of the important 
role that wandering mesenchyme cells play in these processes. The 
problem is also further confused by the perplexing mixture of cells of 
different origin brought about by the early established circulation of 
the body fluids. The development of no other embryonic tissue is so 
disturbed by mechanical and physical conditions. 
A study of living fish embryos with the high power microscope has 
made it possible to observe the behavior of the wandering cells and to 
follow them in their development. The disadvantages due to the inter- 
mixture of cells in the blood current have been overcome by the investi- 
gation of embryos in which a circulation of the blood is prevented from 
taking place. 
When the eggs of the fish, Fundulus heteroclitus, are treated during 
early developmental stages with weak solutions of alcohol, the resulting 
embryos in many cases never establish a blood circulation. In other 
respects these embryos may be very nearly normal and the development 
and differentiation of their tissues and organs often proceed in the usual 
manner, though at a somewhat slower rate. The heart and chief vessels 
are formed and the blood cells arise and develop in a vigorous fashion. 
The heart pulsates rhythmically but is unable to propel the body fluid 
since its venous end does not connect with the yolk vessels. And in 
many cases its lumen is partially or completely obliterated by peri- 
blastic material and nuclei which seem to be sucked into the heart 
cavity from the surface of the yolk. 
In these embryos without a circulation of the blood, one is enabled 
