128 
JANE I. KOBEliTSON. 
shed free rounded blood-cells into the lumen of the develop- 
ing vessels. In the smaller vessels the actual shedding is 
difficult to detect^ but the process is evident enough in the 
heart (Text-fig. 28 a, c and d, en.) 
Blood -cells. — On the surface of the yolk the lateral 
mesoderm is at first only to be distinguished from the under- 
lying endoderm or yolk-cells by the increased number of 
somewhat smaller nuclei and the more finely fragmented 
Text-fig. 31. 
Diagram of a plane surface projection of the cardio-anal hands of 
multinuclear niesoderm. a. anus. 
condition of the yolk-grauules (Text-fig. 29 a, m.) The 
nuclei are generally arranged in one; but here and there in 
two or even three irregular layerS; while the cell margins 
are not sharply defined; the appearance being that of multi- 
nuclear masses of yolk-laden protoplasm (Text-fig. 30 A; m.) 
The doubling or trebling of the nuclear layer occurs 
mostly in little scattered patches over the surface of the yolk, 
but there is one continuous conspicuous band of two or even 
three nuclear layers (Text-figs. 29a and oOa, m.) in thick- 
ness on each side along a line extending from the cardiac 
region backwards and venti ally to the anuS; where it merges 
