812 On Certain Factors of Evolution. 
of inheritance, but occurs in young hatched without the cave, and 
afterwards carried in so as not to be exposed to the light, the shell 
remaining pale as in the very young. Perfectly white, bleached 
specimens of the common Polydesmus granulatus Say, occurred in 
Indian Cave. The pale variety of Tomocerus plumbeus is possibly 
the product of a single or at least very few generations; the white 
and blind Porcellio found by Mr. Hubbard in Little Wyandotte 
Cave, though possibly a true cave form, has not yet been found 
elsewhere, and may have been the young of a normal, epigean spe- 
cies. But the most striking instance is the bleached specimen of 
Asellus communis from Lost River, referred to on pp. 15 and 33, 
which, though white, had eyes of normal size: there is good reason 
to suppose that these specimens were hatched in epigean waters, and 
that being carried into Lost River when young, the pigment in its 
skin, owing to absence of light, had failed to assume its normal dark 
color. 
A parallel case is that mentioned by R. Schneider*:— 
“The author gives an account of the subterranean variety of 
Gammarus pulex which is found at Clausthal. The first point of 
interest is its pale color, pigment being so completely absent from 
its body that it is milk-white and transparent; even the fat-cells, 
which are intensely red or orange-yellow in the ordinary G. pulex, 
are quite white. In the second place, the eye is not normally devel- 
oped, but is in the first stage of reduction; the crystalline cones 
show signs of degeneration, and the whole eye exhibits that ‘ meg- 
alophthalmy,’ or proportionately greater size which is often the first 
indication of loss. The pigment has also begun to be reduced, and 
is of a dirty black, instead of a brownish color. The anterior pair 
of antennæ exhibits elongation, owing to the increase in the number 
of the joints. 
“There is, as compared with the ordinary forms, a considerable 
increase in the amount of calcareous deposits; and there is always 
a considerable amount of iron-oxide in the contents of the intestin®, 
whence the iron makes its way to various parts of the body. 
“ Fries? suggests that experiments should be made on the eltec™ 
1 Unterirdische Gammarus von Clausthal, P. B. Ak. Berlin, 1885, P 
1087; also, Abh. z. Programm k. Real-Gymnasiums Berlin, Ostern ; 
Abstr. in Journal Roy, Mier. Soe. (2), vi., p. 248. 
* Zool. Anzeiger, Aug., 1879, pp. 36, 37. 
effects 
