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BULLETIN OF THE BUREAU OF FISHERIES. 
hand to a man. It gives a stimulation that produces physiological reflexes for the 
moment, and that is small. If the button is carelessly inserted, it might tend to further 
stimulate the skin during the succeeding two or three hours, but the effects even in this 
instance would be so slight that it seems to me there would be no very noticeable influ- 
ence on the fish. Scarcely a fish is caught in the upriver fish wheels where I have 
worked but that shows physical injuries greater than this. 
There still remains the general effect of the handling. No doubt a certain amount 
of fright and stampeding must have resulted from the handling of these fish, just as it 
would have resulted if the same fish had been turned loose directly by the lifting of the 
trap or from a seine. This effect will be discussed more fully in the next chapter. 
EFFECTS OF MARKING ON MIGRATION. 
The question that naturally presents itself is, What effect will all this have on the 
migration and on the manifestations of the migratory instinct of the salmon? In my 
opinion, it will have little or none, and the following pages will reveal my reasons. 
First of all, one must divest himself of the customary attitude toward reactions 
of such complex animals as man and the domestic animals. These are far too complex 
for comparison with salmon. The reactions of a form so low as the salmon must be 
considered in the light of its biological development.® For example, the salmon brain 
is very simple in its type and low in its development. The cerebral lobes are relatively 
small and the so-called cortex layer consists of little more than a single and simple layer 
of nerve cells. That it possesses anything beyond the very simplest of association 
fibers is improbable. With such a low form of brain the salmon can not carry out very 
complex reactions; it has no machinery for such reactions. 
The simplicity of the salmon’s brain when compared with that of a bird or of a 
mammal is like the mechanical simplicity of the spiral screw in the ordinary cannery 
soldering device when compared to the most complicated intricacies of the vacuum 
solderless heading machines. This salmon brain is complicated enough to coordinate 
certain particular functions; for example, the circulation, respiration, muscular motions, 
etc. That the salmon may carry out consecutive nerve reactions such as psychic 
deductions is impossible. To illustrate, when the hole is punched in the tail in the tag- 
ging process, there are slight muscular movements in the region of the tail — local motor 
reflexes. Sometimes, but by no means always, there may be general motor reactions and 
the fish struggles to free itself. There are also momentary inhibitions of respiration 
involving one or two respiratory movements, and, judging by other experiments conducted 
to determine the fact, there are reactions on the circulatory apparatus. All these are 
of the simpler reflexes and are comparatively slight, and disappear within a few minutes 
at most. The mechanical stimulus of inserting the marking button furnishes an occasion 
for the repetition of the whole series of the above reactions, but in a milder degree. If 
one can rely on the observations made on sharks, which are not far removed from the 
salmon in their development, one must conclude that mutilations much more severe 
° F.dingcr.L. : Ueber das Horen der Fische und anderer niederer Vertebraten. Zentralblatt fiir Physiologie, bd. xxii, 
1908, p. 1. 
