Chap. V.] ACCLIMATISATION. I73 



of the Old and Xew Worlds should he closely related, 

 we might expect from the well-known relationship of 

 most of their other productions. As a blind species of 

 Bathyscia is found in abundance on shady rocks far 

 from caves, the loss of vision in the cave-species of this 

 one genus has probably had no relation to its dark 

 habitation; for it is natural that an insect already 

 deprived of vision should readily become adapted to 

 dark caverns. Another blind genus (Anophthalmus) 

 oilers this remarkable peculiarity, that the species, as 

 Mr. Murray observes, have not as yet been found any- 

 where except in caves; yet those which inhabit the 

 several caves of Europe and America are distinct; but 

 it is possible that the progenitors of these several 

 species, whilst they were furnished with eyes, may 

 formerly have ranged over both continents, and then 

 have become extinct, excepting in their present se- 

 cluded abodes. Far from feeling 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 scanty inhabitants of these dark abodes will 

 have been exposed. 



Acclimatisation. 



Habit is hereditary with plants, as in the period of 

 flowering, in the time of sleep, in the amount of rain 

 requisite for seeds to germinate, &c., and this leads me 

 to say a few words on acclimatisation. As it is ex- 



