The brain of Acipenser. 12 
spherical or ovoid nuclei which are placed with the long diameter, 
when such exists, parallel with the basement membrane, i. e. across 
the cell. Each cell is thickest at the part occupied by the 
nucleus, and the nuclei are crowded into two or three irregular rows 
in the lower half of the epithelium. The outer ends of the cells 
are usually separated by some space which is occupied by supporting 
cells, and these latter give to the free surface of the epithelium a 
distinct, smooth outline. Beyond this outline the ciliated cells 
project as slight rounded elevations and upon each of these ele- 
vations is borne a great tuft of cilia. These tufts of cilia are so 
large that they can readily be seen in certain parts of the saccus 
in Phot. 18, in which the magnification is only twenty diameters. 
The cilia are thick hairs from 8 to 12 u in length, and are very 
numerous on each cell. The cilia take a red stain and the outer 
part of the cell often shows a red striation. In GOLGI sections 
these cells are seldom impregnated or are stained in masses so that 
they can not be studied. However, I have found a number of isolated 
cells impregnated and in three cases I have found fibres arising 
from their basal ends and running along the basement membrane 
for some distance. In numerous preparations I have found occasional 
fibres impregnated in the bundles mentioned above. In intra 
vitam methylene blue preparations of the brain of Amiurus in 
which the saccus is small, these ciliated cells are present and oc- 
casional cells are stained with the blue. The nerve fibres are present 
also and I have traced fibres with certainty from the bases of the cells 
into the fibre bundles and on into the inferior lobes (cf. page 123 below). 
The .caudal end of the hypophysis is scarcely in contact with 
the saccus, as seen in sagittal sections. The caudal part of the 
hypophysis has a very different appearance from the cephalic part. 
The caudal one-third lies beneath the epithelial floor of the corpus 
mammillare which has been described above (Phots. 19-—21). The 
whole hypophysis consists of blind sacs or tubes lined by epithelium 
and bound together by a small amount of connective tissue in which 
are small blood spaces. These blood spaces are more numerous 
and larger in the cephalic part. The epithelium is everywhere the 
same, columnar cells with rather large nuclei, both cell body and 
nucleus stained intensely blue. The nuclei are crowded into two 
or more rows and in slightly oblique sections this gives to the epi- 
thelium the appearance of being several layered. The cells are of 
uniform height and there are no cilia present. This epithelium takes 
