10 
FOREST AND . STREAM. 
tJuLV 1900. 
perfect tissues, or are lacking in transparency or develop- 
ment. The contention is that the physical proportions of 
the fish's eye are such that it must, of necessity, be 
myopic, or near-sighted. 
The perfectly formed human eye is a sphere, com- 
plete except at the* front, where the cornea represents the 
segment of a smaller sphere superimposed on the first. 
Fig. I is a diagram of a section or uch an eye, in which c 
represents the cornea, and a and h two parallel rays of 
light entering the eye; 1 is the lens, which has somewhat 
the shape of a disk, hut thicker in the center than at the 
edges — in short, the shape of the ordinary magnifying 
lens so familiar in spectacles, cameras and other optical 
instruments. 
The eye of the fish is, roughly speaking, also made up 
of the segments of two spheres. Its shape, however, is, in 
general, quite difl'erent from the human eye, being much 
.shallower, and the cornea relatively much larger, as shown 
in Fig. 2, where c represents the cornea. The whole eye 
has, in fact, a disk-like shape well suited to the narrow 
heads of fishes, in which the two eyes, flat as they are, 
usually occupy almost the entire diameter of the head. 
The lens of the fish's eye is peculiar. Instead of being 
flattened, or disk-like in shape, it is a perfect sphere, as 
represented at 1. Any one who will take the trouble to 
cut open such an eye will come at once upon the lens. 
It is impossible to mistake it for any other structure; a, 
perfect little ball of crystal, brilliant as a jewel. The 
eye of the fish contains, furthermore, a peculiar structure 
first described by Haller. and named by him the cam- 
panula. It is a muscular body whose function was long in 
doubt, but which has now been demonstrated by Beer tu 
act in such a manner as to draw the lens deeper into the 
eye — that is, toward the median plane of the fish, and at 
the same time, somewhat backward toward the tail of the 
fish. The purpose of this movement of the lens will 
presently be explained. 
It is a matter of common knowledge that the eye and 
the photographic camera take adA^antage of the same 
optical principles: that the eye is, in fact, a camera, into 
which the rays of light pass through the pupil and arc 
gathered to a focus on the retina, or sensitive mem.brane 
which lines the back of the eyeball. At this focus is 
formed a little picture of the object on view, preciseh' as at 
the back of the photographer's camera.- Referring again to 
Fig._ I. we have a and b representing two parallel rays 
of light entering the eye. They first reach the cornea c, 
which, being curved in shape, and more dense than the 
air in which the rays had previously traveled, bends these 
rays so that they approach each other. They next en- 
counter the lens, which, being still more dense, bends the 
rays yet more tOAvard each other, so that by the time 
they reach the retina, r, r, they have met and formed a 
focus at f. 
The point at Avhich the rays are brought to a focus is 
not the same, however, for all distances. The nearer the 
object, the further back in the camera the picture is 
formed. It is, therefore, necessary for . every working 
camera to have some method of adjustment for different 
distances, otherwise a clear picture will be formed only 
when the object is at a certain fixed distance. In the 
manner of securing this adjustment the eye and the 
photographic camera are not alike. Jn the latter the 
bellows-like arrangement of the sides enables the operator 
to lengthen or shorten the camera, so as to place the 
sensitized plate at the focus. Avherever that may be. In 
the human eye, however, the walls are of fixed dimen- 
sions, but the lens is elastic, permitting it, by means of a 
nmscular apparatus, which it is here ixnnecessary to 
describe, to be made stronger or Aveaker as the case Jiiay 
require. In Fig. i has already been traced at a, f, and b. 
f. the course of parallel rays such as come from a distant 
point. The dotted lines proceeding from d represent 
diA'Crgent rays, such as come from a point near at hand. 
If such rays Avere bent only as much as a and b AA^ere 
bent, they obA'iously Avould not meet at f, but would be yet 
some distance apart Avhen the retina, 'r, r, Avas reached. 
To prcA^ent this the elastic lens, 1. almost automatically 
becomes more convex, as indicated by the dotted curA^e, so 
as to bend the rays more toward each other, ,ind there- 
after they travel on the same lines as did a and b, to the 
focus at f. 
Such is, in brief, the method of adjustment of tile 
human eye, technically called the accommodation. Its 
perfection depends entirely on the elasticity of the lens, 
and therefore its limits coincide Avith the limits of that 
elasticity. To illustrate, if the printed page of this paper 
be brought gradually closer to the eye, the lens Avithin 
the latter will become gradually more convex and the 
letters still be clearly seen, because the focus still falls on 
the retina; but soon a point is reached, say at about 6 
inches, Avithin which the letters are blurred, because the 
lens is there at its greatest possible conA'exity. The limit 
of its elasticity has been reached, and within that point 
it is unable to bend the rays stifliciently to bring them to 
a focus on the I'etina. 
The other limit to the elasticity of the lens, which is, of 
course, its point of least couA^exity, can be best illustrated 
by examining the myopic eye, of Avhich Fig. 3 is a diagram. 
The myopic eye is faulty in its proportions. It is not a 
true sphere, the diameter from the cornea, c, to the 
retina, r, r, being too great. Thei'efore, when the parallel 
rays of light, a and b, enter the eye and receive the same 
bendings toAvard each other that were traced in Fig. i, they 
come to a focus at f. Fig. 3, Avhere the retina ought to be 
situated, but AAdiich is really in advance of the position of 
that membrane. Optically speaking, therefore, a myopic 
eye is one in VA'hich the focus is in front of the retina. If 
the lens, 1, cotrld be made less convex the focus of the 
rays, a and b, could be carried backward to the retina, 
but the lens is already at its point of least convexity. The 
only Avajf for such an eye to focus the rays on the retina 
ajid hence to see clearly is to bring the object close to the 
eye, say to the point d, Avhence the rays diverge strongly 
on entering the eye, and tend to a focus further back, 
namely, at f on the retina. Hence, the propriety of 
calling such an eye "near-sighted," the point d represent- 
ing its furthest point of distinct vision. 
One other fact concerning the elasticity of the lens is of 
interest in comparing the fish's eye Avith our OAvn. The 
elasticity of the human lens diminishes Avith age. At 
fifty or fifty-five years of age it has almost disappeared, 
and the lens has become rigid. With the elasticity of the 
lens departs, of course, the accommodation, so that in 
age the hofilial. hurnan, eye can see only distant objects 
clearly. For near objects a glass must be worn which 
lakes the place of the lost adjusting power. 
In the fish's eye flie course of the rays of light may be 
followed by reference to Fig. 2. The parallel rays a and 
b passing through the Avater first encounter the cornea, c. 
Here, it might be anticipated, they Avould be bent tOAvara 
each Other, as was the case in the human eye in its 
natural element, the air. But corneal tissue is of prac- 
tically the same density as water, and Avhen the two are 
in contact, as in the case of the fish, the rays of light pass 
from one to the other Avithout change, and arrive at the 
lens, 1, AA^hich, as previously noted, is of a spherical shape. 
The surface of such a small sphere is of necessity strongly 
curved, and bends the rays sharply toward each other— 
so sharply, in fact, that they meet close behind the lens 
and before they reach the retina, r, r. This formation of 
the focus in front of the retina Avas precisely what 
took place in the myopic human eye. Fig. 3, and is, in- 
Fig. [. 
deed, the essential characteristic of myopia. There- 
i^ore, the fish's eye is properly classed as myopic, notwith- 
standing its general shape is widely different from the 
myopic human eye. 
In the method of adjustment for different distances, 
however, the fish's eye differs entirely from the human 
eye and the eyes of all the higher A'ertebrates. The func- 
t-ion of the campanula of Haller has been already referred 
lo. Through the action of this muscle, the lens, 1, Fig. 2, 
is carried to the position 1', and the focus of a clistant ob- 
j-ect to the position f, which is on the retina. Near 
Fia. J. 
objects, of course, are in focus when the eye is at rest 
and the lens in its first position. There remain no 
grounds for denying that a fish may focus his eye for any 
point from infinity up to a point a fcAV inches in front of 
his cornea. The supports of Cuvier's opinion, Avhich 
are enumerated on our first page, all fail Avhen it is proven 
that the lens can be made to approach and recede from 
the retina. That the myopic eyes of fishes do. in gen- 
eral, possess this poAver can no longer be doubted. Beer's 
experiments in electrical stimulation embraced sixty-eight 
species, from tAventy-tAvo families, and representing all 
Fro. 3- 
the orders of the teleosts. In all the experiments the 
movement of the lens was demonstrated ; indeed, the act 
may be directly obserA'ed in aquarium fish by Avatching 
the eye intentl}^ from above, Avhence a portion of the 
spherical lens may be seen projecting through the pupil. 
The sum of the comparison between the types of eyes 
which Ave have here considered is as follows: 
1. .'Ml the higher vertebrates, including birds, have 
e\-es adjusted naturalh' for distant objects, but contain an 
elastic lens capable of adjustment for near points. In' 
such eyes myopia is a deformity, incompatible Avith good 
sight at any but short ranges. 
2. Fishes have eyes adjusted naturally for a near 
point, but furnished with a movable lens capable of adjust- 
ing them for distant points. With such eyes myopia is no 
longer synonymous Avith "near sight." 
Accepting as proA'en that fish eyes are optically perfect 
for all distances, some interesting speculations are allow- 
al))e as to Avhat they reallj- can see under varying con- 
ditions. Their sight, like our own, is subject, of course, to 
the limitation imposed by the size of the object relative to 
its distance, and is dependent on the clearness of the 
Avater, as is ours on the clearness of the air. It is prob- 
able that fishes, like ourselves, cannot see an object 
clearly Avhen it is brought extremely close to the eye, 
since it is likelj- that their accommodation, like our own, 
does not cover that territory. In one particular the 
peculiar principle on which their eyes are constructed 
gives them an adAJ^antage over their felloAv A-ertebrates — 
namely, their sight is not affected bj' age. It has been 
already noted that the accommodative pOAver in the human 
eye is totally lost at about fifty-fiA^e years of age by 
reason of the rigidity of the lens. An equal loss Avould be 
a greater catastrophe to a fish, because it would leaA'^e him 
Avith an eye adapted only for near vision, and because 
many fishes live far beyond the age of fifty-five years. 
The fish is neatly saved, tioyt'ev^-r. from ^ long age 9f 
myopic decrepitude by the fact his accommodiation never 
depended on the elasticity of his lens, but is accomplished 
by changing the location of the latter. He never be- 
comes _ "old-sighted," and can, presumably, detect the 
angler's cheats as readily at a hundred years as he did 
Avhen a fingerling. 
The ease Avith Avhich a fish in the water can see an object 
•in the air, or with Avhich a man above the water can see an 
object under it, depends on the evenness of the surface 
and the arrangement of the light. The difference in 
density of the tAvo media, provided they are equally clear 
and free from foreign matter, can only change the ap- 
parent location of the object in one medium to the obserA^er 
in the other: it does not affect the clearness of vision. 
The slightest ruffling of the surface, however, by dis- 
persing the rays of light, is rapidly destructive of distinct 
A'ision in either direction. We are perfectly secure in 
asserting that the fish in the water can see a man on the 
bank much better than the man can see the fish, since the 
latter has the advantage of the light, the size of the ob- 
ject looked at, and in the probable color contrasts. 
When, however, Ave consider the vision of the fish in 
the air, or compare it with the vision of the man under 
water, the Avhole aspect of the problem is changed in a 
very interesting manner. As long as the fish remained 
under water, its cornea, as stated previously, being of 
practically the same density as the water, took no part in 
bending the rays of light, and, therefore, could be totally 
disregarded in Fig. 2 and the references thereto. Being 
much more dense than the air, however, the fish's cornea 
comes into play Avhen it is taken from the Avater, and by 
greatly increasing the bending of the rays of light, it 
makes the fish many times as myopic as it was before — ■ 
in fact, far beyond the poAver of its accommodative ap- 
paratus to overcome, so that its theoretical point of clear 
vision is almost in contact with the eye. 
In the case of the man under Avater, the circumstances 
are exactly reversed. So long as he remained in his 
natural element his cornea performed a great portion of 
the bending of the light rays necessarj' to his clear vision. 
When his eye is placed in contact Avith water, the effect is 
optically the same as though his cornea were removed, as 
its action on the rays is abolished because of its not 
differing in density from the Avater surrounding it. In 
his turn, by entering an unnatural medium, he has his 
accommodative apparatus taxed far beyond its pOAver, and 
clear vision becomes impossible. We may reckon, how- 
CA^er, that the departure from a normal standard is from 
fwo to four times as great in the case of the fish as in that 
of the man, so that, as far as may be judged, the human 
eye is better fitted for vision under water than is the 
fish'.s eye for visiort in the air. In point of fact, a diver, 
unarmed with any instrument which protects his eyes 
from contact Avith the Avater, though he sees nothing 
distinctly, is able to make out the general form and 
color of t|uite sm.all objects, and avc may estimate that 
the fish out of water sees half or one-fourth as Avell. 
Boston Anglers. 
Boston, June 30. — Mr. Seth G. Moore died at his 
home in Brookline on Tuesday at the age of eighty years. 
Mr. Moore had always taken great delight in angling, 
and mauA' is the spring trip he had made Avith his son, 
Harry B. Moore, to Moosehead and other Maine Avaters. 
Even this spring he had planned for a trip to Moosehead 
Avitlihis son, but the latter, noting that his father was not 
in his usual health and vigor, discouraged him. But his 
love of angling ncA'er waned, and his many years and 
excellent health he was in the habit of attributing to his 
outings with rod and reel. Only three or four years ago 
he was upset from a canoe at Moosehead, but he clung 
to the frail craft till picked up by other boats, as Avell as 
did cither Harry or the guide, and was none the worse for 
the ducking in the almost ice-cold water. When the 
affair Avas all over Harry had to nearly laugh his sides off 
as he saw his father's pipe still lighted and going. The 
overturn had not sufficiently alarmed the old gentleman 
to cause him to drop his pipe, and he still clung to his 
rod with one hand. 
The trout fishing has taken on all of its usual hot 
Aveather dullness, and the summer boarders are now at the 
fishing resorts in considerable numbers. Not so the 
real angler, for he is off for the salmon waters or is 
fitting out. Capt. John Bryant, well known in yachting 
circles, is off for the Tobique, with his three boys, for 
salmon fishing. Mr. D. H. Blanchard, Avith his friend. 
Mr. Winsor, of Philadelphia, has gone to his salmon 
river, the NortliAvest Branch ot the St. Marguerite. Mr. 
Blanchard has visited this river, which he owns, with his 
family and invited guests, for many seasons. The late 
Mr. Keeler, of Boston, was his beloved fishing friend for 
many seasons. His river is peculiar from the fact that it 
is at the foot of tremendous boulders in a rocky gorge, 
up over Avhich the salmon do not go. Mr. H. K. Peaver, 
of Boston, has gone up the Saguenay salmon fishing. 
Mr. Henry R. Reed, of Boston, Avho has fished the Ris- 
tigouche for several seasons, with Senator Aldrich, will 
have Senator W. P. Frye for his salmon fishing compan- 
ion this season, for the good reason that Senator Aldrich 
has gone to Europe. Senator Frye did not find the trout 
fishing at the Rangeleys all that he could wish, and 
doubtless is willing to try for something larger in the 
riA^er that has been fished by no less personages than 
Henry Ward Beecher, Chester A. Arthur, Chief Justice' 
Gray, and last, but not least, that editor of the Albau}' 
Evening News for many years, who Avrote the charming 
'book, "The Pleasures of Angling." The Hon. George 
Von L. Meyer, a Boston member of the Ristigouche 
Club, has gone to that river. Mn A. N. Parlin, of Bos- 
ton, is fishing good salmon waters on the St. John. Mr. 
E. C. Fitch, of Waltham, has gone to his salmon river, 
the Romaine. Mr. J. T. Spaulding, Avith Mr. Henry P. 
King, has gone to upper Ristigouche Avaters for salmon. 
It is generally agreed among salmon fishermen that so 
far only a very few fish have been taken, but they count 
that it is early yet. The old salmon pool at Calais, Me., 
however, is reported to be turning out some good salmon. 
Dr. F. M. Johnson, of Boston, has taken tAVO handsome 
salmon there recently. Those interested say that the 
salmon fishing is likely to hold out all the season there, 
as it did last year, after several years of poor fishing. 
The Pan^ov, M?„ sailtpo^l pool heis aiuounted to almost 
