10 
INTRODUCTION. 
relative importance of Zoological differences as when the looal circumstances con¬ 
nected with them are taken into account. Where I have overlooked facts, or 
failed in my conclusions concerning them, I must crave that indulgence which is 
never denied to the honest inquirer even in a field so small as that throughout 
which my researches have been prosecuted,—researches which I am well aware 
can at the best add hut an iota to our knowledge, 
“ A drop dissevered from the boundless sea.” 
