The Scottish Naturalist. 103 



enough, but with the other part of this section there is a consider" 

 able amount of difficulty. In the first place a uniform standard 

 is required by which the comparative abundance (or the reverse) 

 of a species can be judged. In the second place, the terms in- 

 dicating the comparative abundance must have definite meanings, 

 and not be used indiscriminately. It is probable that in many 

 cases a species may happen to be abundant in one area, and rare 

 or absent in others. The terms indicating the abundance will not, 

 moreover, stand as signifying independent facts, but must always 

 be controlled by the statements as to the habitat and the vertical 

 and horizontal ranges. For instance, supposing we have a species 

 indicated as "common" in all three areas, we must not jump to 

 the conclusion that it is common throughout the whole of these 

 areas, but looking to the statement of the habitat, find that it is a 

 species of the sea-shore. " Common " in this case would, there- 

 fore, mean common wherever the nature of its habitat permitted 

 it to occur. 



It will be desirable, therefore, to have a code of terms with de- 

 finite meanings drawn up before the catalogues are taken in hand. 



Another point in this section demands attention. As you are 

 aware, not all the animals and plants that now appear to be 

 " natives " of this country are really indigenous inhabitants, but 

 some of them have been introduced— accidentally or purposely — 

 by the agency of man. In some cases it is easy to decide whether 

 a species is native or naturalised, but in others it is a matter of 

 considerable difficulty. Moreover, there are degrees of naturalisa- 

 tion — some species having been long and thoroughly established ; 

 others only endeavouring to make good their footing, and still 

 struggling for a place. It is important, therefore, that an opinion 

 should be expressed as to the nativity or otherwise of the species, 

 and its degree of naturalisation if a naturalised one. 



5. Distribution outside the District. — It may be assumed that 

 not many species (if indeed any) are really restricted in their dis- 

 tribution to the district, but that they also occur elsewhere. What 

 their distribution is outside, has in many cases an important bear- 

 ing upon their distribution inside the district ; and it is, therefore, 

 desirable that some information at least should be given as to this. 

 Such information will relate to the distribution in Britain, and to 

 the distribution elsewhere. It need scarcely be mentioned that 

 minute details of the exotic distribution are not necessary. 



