INTRODUCTORY CHAPTER. 





readers, let it be understood that the -whole is merely brought forward as a conjecture, to which, 

 whatever data we have been able to collect being given, we leave our readers to decide with regard 

 to the probability or the contrary of it. Should it, however, prove true that many now supposed 

 species, inhabiting different countries, are the same, and merely varieties, it will not lessen in any 

 degree, or make less interesting or important, the labours of the zoologist ; for, in an intellectual 

 point of view, can anything be more interesting than to unravel what appears to be a mystery, and, 

 in an useful one, to point out such animals as will breed together, and thereby open the way to 

 improvement in our varieties of domesticated animals. 



In the internal arrangements of the group we intend to illustrate we shall deviate from the 

 course followed by other authors, and propose one which, as far as we have been able to carry 

 our investigations, appears to be in harmony with both the external and internal organization 

 of each genus. We must here mention it as a subject of regret, that, although our utmost 

 endeavours have been used, we have been totally, on account of their rarity in this country, unable 

 to obtain either subjects for dissection, or even a sight of the skeletons, of many Genera. 



Many parts throughout the group appear to be in favour of Mons. Temminck's opinion, that 

 there are no such divisions as Genera in nature, the transition from one extreme of form to another 

 being so gradual that it is difficult to say where to draw the line of division. 



Upon a minute examination, however, as far at least as we are at present acquainted with the 

 species, there is always found some break as it were between the forms constituting contiguous 

 Genera or Subgenera, and some tangible distinction between them, although in many particulars 

 they appear closely to approach. It is probable, however, that many new forms will yet be dis- 

 covered ; therefore, in the present state of science, it is impossible to say whether this opinion of 

 Mons. Temminck's will eventually prove true or not. Should it be correct, a serious difficulty 

 will arise with regard to nomenclature, in designating the objects to be named by a specific 

 appellation alone. If we do not admit Genera we cannot admit families, orders, or classes ; the 

 transition will, therefore, we contend, be complete through all, before we can abolish the one or the 

 other. 



We shall now add a few words on the characters we have employed. Measurements are 

 always subject to a certain degree of variation ; we have, therefore, when the opportunity has 

 offered, given a mean of two or three. The number of tail feathers is far too variable a character 

 to be admitted into any ornithological work. We have now before us three specimens of Erismatura 

 rubida, in which, although in this genus the tail is an important member, the numbering of each 

 differs. We have, for the first time, as far as we are aware of, made use of anatomical characters 

 for divisions, taken from the trachea and skeleton principally ; this has not been done without due 

 consideration, and the examination of a great number of specimens. 



We have no doubt that some will find fault with us on account of the shortness of the 

 descriptions at the head of each specific character, the use of these, at least what we have supposed 

 it to be, is, that in looking over a large number of descriptions we may readily catch some mark 

 whereby the object we wish to name may be distinguished, perhaps, in common with one or two 

 others from its congeners, and thus that the time taken to read over a large number of long 

 descriptions will be saved. 



The characters of the Genera, and the cuts of bills and feet, are invariably taken from the 

 species w^e have named as the generic type, unless it is mentioned to the contrary. 



