MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 
123 
As regards Dr. Joseph’s Gambarus stygius, based on an imperfect specimen from a cave in 
Carniola, it appears that it is still uncertain, from a strictly systematic point of view, whether 
it is a genuiue Cambarus or Astacus, as Dr. Joseph does not say whether it comforms to the 
genus Cambarus in the number and arrangement of the gills or not. Joseph states that the hooks 
spring from the second segment of the leg, but Professor Faxon thinks this is an error, since 
in Cambarus these processes are always found on the third segment. Joseph apparently refers 
it to the genus Cambarus from its close resemblance to G. pellucidus, especially in the shape of 
the body and the form of the non-facetted eyes. So good an ob server as Joseph would scarcely 
have made a mistake as to the position of the hooks, and thT57"at any rate, can scarcely be a char¬ 
acter of importance. Systematists may carry trivial characteristics too far, and we do not see why 
the profound modification of the eye, involving the absence of corneal facets, of rods and cones, 
and of a genuine pigment, as well as the greater slenderness of the body and limbs, are not suf¬ 
ficient characters to isolate these three blind species under the name Orconectes, especially since 
there are no series of half or partially blind forms connecting the blind and normal species. On 
the other hand, no one doubts but that the American species of Orconectes has been derived from 
Cambarus, though the facts have not yet been discovered to show that the Carniolan species may 
not have been derived from the European Astacus.* 
Finally, as regards all the eyeless genera in question, I do not see how we can in our system 
put nature into a straight-jacket, and regard as simply of specific value the loss of eyes, sometimes 
involving the total abolition of optic nerves and optic ganglia. It is a convenience not to lump 
such forms with a mass of other species, where they will lose their individuality, but rather to 
emphasize them by giving them distinct generic or at least subgeneric names. 
COMPENSATION FOB THE LOSS OF EYES OB EYE-SIGrHT. 
As has been observed by some who have written upon cave animals, the atrophy of the eyes 
and consequent loss of vision have been made up, in part at least, by a corresponding hypertrophy 
of the organs of touch and smell. 
The more apparent anatomical modifications of the Arthropods consist in the greater slender¬ 
ness of the body and the increased length and tenuity of the antennae and limbs. 
In the planarian worms, however, there seems to be no other change than the loss of eyes 
and a general albinism or degeneration of the pigment cells. 
Compensation by increase in the sense of touch. —It is in the Arthropods, whether Crustacea, 
Arachnida, or insects, that we see the most marked change in the form of the body and its append¬ 
ages. When we compare the American species of Ctecidotaea with Asellus the body is seen to 
be much attenuated, and the antennae much longer and slenderer, as well as the legs. The genus 
Orangonyx, according to Bate and Westwood, is nearest allied to a marine genus, Gammarella, 
but the European species (C. subterraneus) have shorter antennae than the two species of Gamma¬ 
rella figured in the “ British.Sessile-eyed Crustacea.” On the other hand, the antennae of C. anten- 
natus of Nickajack Cave are longer than in any American or European species known to us. 
In the eyeless species of Niphargus the body is much slenderer than in the species of Gamma- 
rus, and though the antennae are no longer, the last pair of uropoda are remarkably long and 
slender. 
In the two species of blind crayfish the body is longer and slenderer than the normal Cambari; 
the legs are slenderer, particularly the hands, while the antennae are not longer in proportion to 
the body than some species of Cambarus. Eyeless Myriopods, especially Pseudotremia and Sco- 
terpes, have longer antennae than in epigean species. 
Coming to the blind Arachnida, the bodies of the blind Chernetidae tend to become much 
longer, slenderer, and the cheliceres, as well as legs, much longer than is normal. This great 
length of the legs, which may be regarded as tactile organs, enabling them to be used for sound¬ 
ing objects, is most marked in Phalangodes armata when compared with the Coloradan P. 
robusta. 
* It may be observed that in his “Etudes” on Phyllopodes, in referring to Joseph’s eyeless eave Branchipus pelluci- 
dus, M. Eug. Simon remarks: “Espfece aveugle qui deviendrd, sans doute le type d’un genre special.” 
