128 
MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 
In their native pools and in the aquarium when disturbed they do not strike the bottom or sides of their surround¬ 
ings, but seem to have a sense of resistance (if the term is pardonable) which protects them. I can only regret that 
I have not examined those recently caught to ascertain the nature of their food. I never observed any excrement 
voided by them. 
Though the ears of Amblyopsis are said by Wyman to be “largely developed” and the oto- 
lite of the vestibule “quite large when compared with that of a Leuciscus of about the same 
dimensions as the blind-fish,” yet according to Dr. Sloan’s statement this fish is not sensitive 
to sounds. As he is a good observer, and has kept these fish iu a large, spacious tank for 
twenty months, where I have seen them, his observations must be relied upon. Dr. Wyman, 
however, remarks: “It is said that the blind-fishes are acutely sensitive to sounds as well as to 
undulations produced by other causes in the water.”* * * § It is evident that further experiments on 
living blind fishes as well as more extended anatomical investigations are needed to settle the 
question whether the fish are generally seusitive to sound. It may be said in this connection that 
so far as is known most of the cave Arthropods, at least the insects, are not provided with organs 
of hearing, the olfactory being the prominent sense in eyeless insects. On examining the audi¬ 
tory sacs of Orconectes hamulatus and comparing them with those of an undetermined species of 
Cambarus with normal eyes, they are about one-third smaller, while the auditory set® are remark¬ 
ably small, being only one-third as long as in the Cambarus with normal eyes, while the hairs are 
only about as long as the seta is thick; whereas in the normally eyed Cambarus the hairs are 
very long, being from six to eight times as long as the seta is thick. Hence we infer that the ear of 
Orconectes is degenerate and the sense of hearing nearly if not quite obsolete. The ear of 0. pel- 
lucidus, from a cave in Indiana, is also mueh reduced in size, being about as large as that of 
0. hamulatus .t (Compare PI. XXI, figs. 4, 5, and 6.) 
In the mole,| which has minute eyes, the sense of hearing, and probably of touch, compensates 
for the loss of eye-sight, which is of no advantage to it in its subterranean life. 
In the Spalax of eastern Europe and western Asia, a mammal not a troglodyte, but living a 
subterranean life like a mole, we have, according to Dr. Duchamp, an interesting case of compen¬ 
sation for the loss of vision. The eyes are so atrophied, being covered by the skin, that this 
rodent is said to be practically blind, but as a compensation the sense .of touch residing in the 
hairs situated about the mouth is exalted, while the auditory passage and internal ear are nor¬ 
mally developed, though the outer ear is wanting.§ 
* If these Amblyopses be not alarmed, they come to the surface to feed and swim in full sight, like white aquatic 
ghosts. They are then easily taken by the hand or net if perfect silence is preserved, for they are unconscious of 
the presence of an enemy except through the medium of hearing. This sense is, however, evidently very acute, for 
at any noise they turn suddenly downward and hide beneath stones, etc., on the bottom (Cope, Amer. Naturalist, 
vi, July 18, 1872). 
t In a Cambarus 50 mm long from the tip of the rostrum to the end of the telson, with normal eyes, the basal 
joint of the first antenn® is 4.5 mm , while the length of the ear capsule is 2 mm ; in 0. hamulatus, 45 mm in length, the 
basal joint is 2.8 mln in length, and the length of the ear capsule is 1.4 mm long; in an 0. pellueidus from Indiana 40 n '“> 
long the basal joint is 2.2 mm long and the auditory sac about 1.5 mm in length. It thus appears that the basal joints 
or scape of the first antenn®, as well as the ears, are much smaller in proportion in Orconectes than in the Cambarus 
with normal eyes. 
t Savi has described “ une varidtd complfetement aveugle,” Duchamp, l. c. “ The eyes of moles and of some bur¬ 
rowing rodents are rudimentary in size, and in some cases are quite covered up by skin and fur. This state of the 
eyes is probably due to gradual reduction from disuse, but aided perhaps by natural selection. In South America a 
burrowing rodent, the tuco-tuco or ctenomys, is even more subterranean in its habits than the mole; and I was 
assured by a Spaniard who had often caught them that they were frequently blind; one which I kept alive was cer¬ 
tainly in this condition, the cause, as appeared on dissection, having been inflammation of the nictitating membrane. 
As frequent inflammation of the eyes must be injurious to any animal, and as eyes are certainly not necessary to ani¬ 
mals having subterranean habits, a reduction in their size, with the adhesion of the eyelids and growth of fur over 
them, might in such case be an advantage; and, if so, natural selection would constantly aid the effects of disuse” 
(Darwin’s Origin of Species). Also compare foot-note on p. — . 
§ Maissi 1’ceil du Spalax, caehd sous la peau, est incapable de remplir ses fonctions, deux autres sens, I’ou'ie et 
le tact, largement ddveloppds, viennent supplier h l’absence du premier, disposition d’autant plus intdressante qu’elle 
est constante chez toutes les espbces de la faune souterraine. 
Tons ces poils raides qui hdrissent les bourrelets cdphaliques et la region circumbuccale, probablement aussi 
ceux qne l’on rencontre h la pdriphdrie des pattes antdrieures, sont autant d’organes tactiles qui, multipliant les sen¬ 
sations, ne permettent ;) aucun corps de passer inapergu. 
L’cei) demeurant sans exercice s’est atrophid, le pavilion auriculaire qui genait l’animal dans l’intdrieur de ses 
