/232 Miscellaneous. 
inferior blastodermic lamella, which still remains for a time united to 
the superior lamella by filaments. Then the axial lamina of Remak 
is formed, in which M. His distinguishes three parts :—1, a layer 
detached from the superior blastodermic lamella; 2, a layer de- 
tached froin the inferior lamella; and, 3, an axial cord of union 
between these two layers. The first two of these parts (inferior and 
superior accessory lamine) are characterized by vertical strie. The 
third is designated by M. His the azial cord. These parts give origin 
to the medullary tube, the dorsal cord, the protovertebree, and the 
cephalic and lateral plates. The first indication of the place where 
the descending aortze will subsequently be situated appears in the 
form of lacunze behind the rudiments of the protovertebree. The 
situation of the heart is marked by a similar lacuna. 
As the superior blastodermic lamella sends prolongations down- 
wards into the pellucid area, it sends perfectly similar ones into the 
opaque area. But then these prolongations do not form, properly 
speaking, a continuous lamella, but they penetrate the subjacent 
stratum of white vitellus, to form in it a sort of network embracing 
in its meshes the elements of that vitellus. The tissue thus formed 
receives from the author the name of circumvallatory tissue (Keim- 
wallgewebe). Subsequently, in the central part of the opaque area, 
the superficial layer separates to form the vascular area, whilst the 
peripheric adherent portion forms the vitelline area. 
In the interior of the circumvallatory tissue there now appears, 
According to the author, a complete system of lacunze, which, speedily 
opening one into the other, cut off a thin superior layer. This sends 
off filiform prolongations both upwards and downwards. It is the 
hematogenous membrane, formed of cells of the archiblast united 
into a network of which the meshes. enclose bundles of cells of the 
white vitellus. These packets of cells are the starting-points of 
the formation of the blood-vessels: fusiform cells start from them — 
to penetrate into the subjacent lacune and clothe them with a 
continuous endothelial layer; thence they enter the pellucid area, 
where they extend themselves in the lacunee between the inferior 
accessory lamina and the inferior blastodermic lamella; finally, con- 
tinuing their centripetal advance, they introduce themselves into the 
cardiac and aortic lacune mentioned above, where they arrange 
themselves in a coil, which merely applies itself to the walls of these 
lacunze without becoming amalgamated with them. From these 
primitive vascular walls are subsequently developed all the rudi- 
ments of vessels, as also the mass from which are derived the con- 
nective and cartilaginous tissues, and in general all the conjunctive 
tissues. We may therefore say that, from a genetic point of view, 
all the conjunctive substances may be assimilated to the adventitious 
tunics of the vessels.— Archiv fir mikrosk. Anat. Band ii. p. 513; 
Bibl. Univ, August 25, 1867, Bull. Sci. pp. 330-332. 
