Blind Victorian Freshwater Crustacea, 563 
animals that are not inhabitants of caves (3). From a study 
of this list it may be seen how very exceptional is the absence 
of eyes in orders and classes of animals in which they are 
generally present, other than inhabitants of dark caverns, 
subterranean water, or ocean and lake abysses, but that there 
are exceptions must not be forgotten. In the order Amphi- 
poda there are no blind forms recorded from lighted situations 
in the list just mentioned, and I am unaware of any other 
than the present instance of widely separable forms, each 
being blind, living and breeding in one place amongst normal 
surface-forms. 
That they possess the peculiar characteristics of a subter- 
ranean or cave life—viz. loss of eyes and want of colour, 
to which may be added slenderness of form,—will, from the 
foregoing, be obvious; and when it is remembered that they 
belong to widely separated groups and are found in the same 
locality, one is justified in assuming that their near ancestors 
were inhabitants of subterranean waters or caves; but how 
long since such was their habitat and in what way the change 
_has been accomplished I am unable to offer any opinion. It 
is at least clear that they have been and are still successful 
in the sharper struggle incident to a surface-life; and on 
account of this one would expect to find greater modification 
of sensory organs, to endow greater sensibility, than in the 
subterranean forms, where there are so few competitors. 
This, however, does not appear to be the case except in the 
Niphargus, in which the terminal pair of uropoda 1s charac- 
teristically increased in length. As previously stated, there 
does not appear to be any appreciable difference in the 
number of olfactory and auditory seta. Regarding the other 
two species, it must be remembered that they are Isopods and 
that the members of this group are normally frequenters of 
secluded situations. 
To say how longa time has elapsed since the blind Thorp- 
dale species have inhabited total darkness such as would 
have led to entire atrophy of the eyes would be pure specu- 
lation, for there appears to be no data to reason from. Any 
subterranean waters that may exist in the locality must, on 
geological evidence, be quite local, for the extensive Silurian 
area mentioned as existing less than 20 miles northward 
would prevent the possibility of remote subterranean waters 
reaching this locality. Neither is there any evidence, nor 
indeed is there any probability, of any large cavernous recesses 
existing either at the surface or underground. 
Asa matter of interest, certainly not for comparative deduc- 
tion, I may mention that Packard, for one, quotes several 
