Re H? Whitehead’ = 353 
long for the study of the cortex. He detected the anlage first in pigs 
of 2 cm. in the shape of a projection on the medial side of the Wolffian 
body. Ventral from this projection, he says, the coelomic epithelium is 
highly developed; it shows, however, no differentiation, being similar 
to the epithelium of the coelomic cavity in general. This finding, he 
thinks, warrants the conclusion that the cortex is derived from the 
coelomic epithelium. Of the medulla Wiesel makes a more thorough 
study. He traces its origin back to the sympathetic ganglia, and de- 
scribes the passage of medullary cells in collections through the cortex 
to the vicinity of the central vein in the way previously described by 
Flint. 
Fig. 2. Pig13mm. Leitz obj. 3, oc. 4. Ad., adrenal; G. r., genital ridge, Mes., 
mesentery; W. 6., Wolffian body. 
It will be convenient to consider the genesis of the cortex and medulla 
separately, as they are separated by a considerable interval of time. 
THE HISTOGENESIS OF THE CORTEX. 
Although the anlage appears at a much earlier stage, it will be con- 
venient to begin the observations in an embryo of 13 mm. and trace it 
towards its beginning. In such an embryo (Fig. 2) the anlage con- 
sists of an ovoid collection of cells situated ventro-lateral from the aorta 
and dorsal from the angle formed by the junction of the ventral 
