Ramsey, Optic Lobes of Amblyopsis. 41 
hemispheres are larger in Amblyopsis than in the average of 
normal brains. The brains of Campostoma anomalum, Percina 
caprodes, Eupomotis gibbosus and Amblyopsis were measured 
with regard to the comparative widths of the optic lobes and 
the hemispheres. Five fishes of the same length were taken 
of each species. The averages obtained are as follows : 
C. anomalum| E, gibbosus | P. caprodes | A. spelzeus 
Opt. lobes 5. mm 5 mm 6.4 mm 3-2 mm 
Hemisph. 2.5 mm 3.7 mm 3.5 mm 4. mm 
Comp. widths} 56% TAA 54% 125% 
It is thus seen that the hemispheres are relatively larger in 
the blind fish than in the more normal forms, and that the optic 
lobes are relatively much smaller in the former. 
There is no noticeable variation in the cerebellum. In 
length there is a marked shrinkage, chiefly in the optic lobes as 
shown by the position of the cerebellum, which lies directly on 
the lobes (Fig. 3, V). In the normal brain, the cerebellum is 
situated well back, hardly reaching the lobes (Fig. 5, V). The 
following table gives an idea of the length of the brain as com- 
pared with the length of the fish. The brain length is meas- 
ured from the tip of the olfactory lobes to the posterior part of 
the cerebellum: 
Species Length body Length brain | % Average % 
Amblyopsis I g2 mm 5.5 mm 6. G 
oe 2 80 mm 5.3 mm 6.6% 
as 3 go mm 5.5 mm 6. % 
es 4 88 mm 5.6 mm 6.6% 
SC 5 80 mm 5.2mm 6.5% 
nS 6 10) mm 6 mm 6. % 6.3% 
Campostoma I 88 mm 8.5 mm 9.6% 
ec 2 103 mm 9. mm 8 7% 
sf 3 72mm 7.5 mm 10 % 
GC 4 68 mm 7. mm~ 10. % 
On 5 58mm. 6.3 mm 10. % 9-8% 
The result shows the brain of Amblyopsis to be only two 
thirds as long as that of Campostoma. This shrinkage in width 
and length is great enough to show itself in the extent to which 
the cranial cavity is filled. A great depth of fatty tissue covers 
