54 
bulletin of the bureau of fisheries. 
sunlight is thrown into the eye or the surface of the cornea is bathed with even so stimu- 
lating a solution as normal sulphuric acid. The protection apparently is only against 
mechanical injury. 
The second general tactile region includes the whole surface of the fish from the 
posterior edge of the orbits to the pelvic fins except the ventral surfaces of the pectoral 
fins and the skin on the breast between these fins. The second region is bilaterally divided 
and a stimulus applied to any part of one side may call forth a movement of the two dorsal 
fins, the caudal fin, and the anal fin away from that side, an upward movement of the 
pectoral and pelvic fins of the stimulated side, and a downward movement of those of the 
opposite side, a group of coordinated movements already described by Lee (1898). 
These movements are undoubtedly concerned with guiding the fish in swimming. 
The third general tactile region extends from the pelvic fins to the end of the tail. 
This region, like the preceding one, is bilaterally divided. The same fins that respond to 
the stimulation of the second region also respond to stimuli applied to this region, but the 
response is in the reverse direction. A stimulus applied to one side of this region calls 
forth a movement of the median fins toward that side, a downward movement of the 
paired fins of the same side, and an upward movement of those on the opposite side. 
Comparing this condition with that of the second region, it is clear that the fin responses 
produced by stimulating a given side in the second region agree with those called forth 
by stimulating the opposite side of the third region. This diagonal relation is probably 
significant in the swimming movements of the dogfish. 
The fourth tactile region is the ventral surfaces of the pectoral fins and the breast 
region. Mechanical stimuli applied to almost any part of these surfaces call forth a 
fairly symmetrical ventral approximation of the pectoral fins. At times there is almost 
an overlapping of the posterior median edges of the two fins, but never a scissors-like 
movement, such as Sheldon (1909) has demonstrated by chemically stimulating the 
breast region. 
The fifth region is the ventral surfaces of the pelvic fins. When these surfaces are 
stimulated a symmetrical movement of the pelvic fins toward the median plane takes 
place, thus closing the cloaca. There is some correlation between the response of this 
region and that of the fourth, though in the main the two regions are independent. 
The movements of the fins produced from the fourth and fifth region partake of 
the nature of protective movements in that they wipe surfaces or close apertures. They 
probably have little to do with locomotion. The reactions initiated in the second and 
third regions are chiefly locomotor and probably have little significance otherwise. In 
this connection the movements of the posterior dorsal fin are significant. This fin moves 
with extreme freedom and in such a way that its posterior finger-like tip is wiped over 
the back of the animal on the side stimulated as though it were intended to remove 
some offending body. If, however, a weak stimulus is applied to a point low down on 
one side of the body, the fin thus made to move slightly to one side, and then a strong 
stimulus is applied between the dorsal line and the fin, the fin instead of wiping back 
over the newly stimulated part turns still further away from the dorsal line and vigor- 
ously wipes a part of the skin to which no stimulus whatever has been applied. It is 
