The brain of Acipenser. 103 
point of origin of the neurite is sometimes removed from the cell 
body by a distance equal to four-fifths of the thickness of the tectum, 
or twenty times the length of the cell body itself. In these cases 
the point of origin of the neurite is much nearer to the end of the 
dendrite than to the cell body. In the case of the larger cells whose 
dendrites branch near the cell, the neurite arises from the dendrite 
at no great distance from the cell body. Compare Fig. G with Phots. 50 
and 51. The neurite usually rises toward the surface along with 
the branches of the dendrite, gives off some branches, recurves into 
the deeper parts of the tectum and breaks up in numerous end branches 
within the outer one-third. 
In rare cases the neurite 
breaks up in the middle 
one-third of the tectum. 
Type B: cells with ra- 
dially directed dendrites and 
long neurite. I have found 
in a few cases cells which 
cannot be distinguished 
from those of type A, ex- 
cept that their neurites 
seem destined to some point 
beyond the tectum. The 
neurite comes from the den- 
drite, rises to the surface 
of the tectum and turns 
laterad or cephalad in the 
superficial fibre zone. It is 
probable that these fibres 
enter the optic nerve and go 
to the retina (cf. pages 198, 
200). 
Type C: cells of the 
torus longitudinalis Halleri. 
The cells bordering on the 
cavity near the dorsal de- Fee aa Lk RR 
cussation bear a certain Fic. G. 
resemblance to cells near ; 
the mid-ventral line in the hypothalamus and fore brain, to 
be described later. The cell body measures 8—12 by 14—32 w 
