6 INTRODUCTION. 



must have recourse to the authors who treat of it It Is only 

 when (as in the case of the mites, for example,) there is no 

 general work treating of a particular branch of the subject that it 

 has then been gone into with some greater attempt at detail ; but 

 the collection is arranged according to the most approved modem 

 system, with this qualification, that it has sometimes, though 

 rarely, been made to bend so far as to bring together the species 

 of one group, that attack one particular kind of plant, instead of 

 dispersing them among several according to their structural 

 peculiarities. 



Where a cypher (o) is appended to any object in the Catalogue, 

 it means that specimens are intended to be placed in the col- 

 lection but have not yet been procured. 



Andrew Murray. 



