SHAPE OF THE NUCLEUS 599 
The intranuclear canaliculus of nerve-cells (see Text-figs. 7 
and 8) is sometimes demonstrated by the Cajal method for the 
Golgi apparatus, and has apparently been observed by Cajal 
himself. With standard cytological stains—such as iron 
haematoxylin—it appears as a single invagination of the 
nuclear membrane. Its aperture is often opposite the point 
TEXT-FIG. 7. 
Binucleated sympathetic ganglion cell from rabbit. 
Intranuclear canal in one of nuclei. 
TEXT-FIG. 8. 
Pyramidal cell from cerebral cortex of guinea-pig. 
Ap, Apical dendrite; Nc, Intranuclear canal; Ns, Niss] substance. 
of insertion of the apical dendrite in the case of pyramidal 
cells (see Text-fig. 8). In these elements the relation of the 
canaliculus to the centrosome is obscure, largely owing to the 
uncertainty of the existence of this structure in adult nerve- 
cells. 
Intranuclear canaliculi are also readily observed in the cells 
lining the Wolffian ducts in Amphibia, while apparently similar 
structures can sometimes be seen in the tissues of the higher 
Vertebrates, though here, except in the case mentioned above, 
the small size of the cells renders observation difficult, 
