And this is the case with some of the American
cave-animals, as I hear from Professor Dana; and some of the European
cave-insects are very closely allied to those of the surrounding
country. It would be most difficult to give any rational explanation
of the affinities of the blind cave-animals to the other inhabitants
of the two continents on the ordinary view of their independent
creation. That several of the inhabitants of the caves of the Old and
New Worlds should be closely related, we might expect from the
well-known relationship of most of their other productions. Far from
feeling any surprise that some of the cave-animals should be very
anomalous, as Agassiz has remarked in regard to the blind fish, the
Amblyopsis, and as is the case with the blind Proteus with reference
to the reptiles of Europe, I am only surprised that more wrecks of
ancient life have not been preserved, owing to the less severe
competition to which the inhabitants of these dark abodes will
probably have been exposed.
ACCLIMATISATION.
Habit is hereditary with plants, as in the period of flowering, in the
amount of rain requisite for seeds to germinate, in the time of sleep,
etc., and this leads me to say a few words on acclimatisation. As it
is extremely common for species of the same genus to inhabit very hot
and very cold countries, and as I believe that all the species of the
same genus have descended from a single parent, if this view be
correct, acclimatisation must be readily effected during
long-continued descent.
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