16 INTRODUCTORY. 



has indeed gone on for so many years, that it is hard to 

 know where to begin and where to leave off. The case of 

 both our rats, the black and the larger brown, misnamed 

 Norway or Hanoverian, illustrates the difficulty. We have, 

 by contrast with the more recent introduction of the latter, 

 come to regard the weaker species as a much older resident 

 of these islands, which, in point of fact, he is. But this has 

 become so strong in the minds of some, that a recent writer 

 on the subject of ferrets alluded to the black rat as "the 

 oldest inhabitant of this country," and this too w^hen it 

 was introduced from the East in all probability not earlier 

 than the fourteenth century ! Thus, in addition to the 

 species introduced by man, the classification is complicated 

 by others that have arrived in ships or otherwise, but not 

 under his auspices. This is a difficulty which it is im- 

 portant to grasp, because we shall more than once be con- 

 fronted by it in the following pages. 



To make this still clearer, I will give one instance. It 

 will be observed that I have, contrary to the usual practice, 

 omitted the turtles from the list of British vertebrates. I 

 think I should scarcely have ventured, on my own respon- 

 sibility, to do so, had it not been for a trivial episode that 

 I shall relate as my justification. My ship was nearing 

 the end of a long voyage. We had covered 15,000 miles 

 of sea, and had brought successfully through every degree 

 of climate, from a tropical summer to a British winter, 

 two leather-back turtles, which were allotted private 

 quarters in the long-boat, and played on with the hose 

 under my supervision twice a -day. Thus they thrived 

 exceedingly, until, not a hundred miles south-west of the 

 Eddystone, one got washed overboard. The captain, to 

 whom they had been tendered as an advance Christmas 

 gift by one of the Company's agents, raved and stormed 

 in language suitable to the occasion ; but my own regret 

 at his discomfiture was largely tempered by curiosity as 

 to whether the creature might perchance get washed 

 ashore alive, in which case nothing would, if we may 



