INTRODUCTION II5 
Lastly we arrive at the Passrrss, and here, as already mentioned, the 
researches of Garrod and Forbes prove to be of immense service. It was 
of course not to be supposed that they had exhausted the subject even as 
regards their Mesomyodi, while their Acromyodi were left almost untouched 
so far as concerns details of arrangement ; but later investigations have 
produced a much more manageable scheme, and so far as it is goes Dr. 
Gadow seems to have good reason for the groups he has made, even though 
exception be taken to part of his nomenclature, 
Thus we reach the true Oscines, the last and highest group of Birds, 
and one which, as before hinted, it is very hard to subdivide. Some two 
or three natural, because well-differentiated, Families are to be found in 
it—such, for instance, as the Hirundinide (SwatLow), which have no 
near relations ; the Alaudidx (Lark), that can be unfailingly distinguished 
at a glance by their scutellated planta, as has been before mentioned ; or 
the Meliphagide (HONEY-EATER), with their curiously constructed tongue. 
But the great mass, comprehending incomparably the greatest number of 
genera and species of Birds, defies any sure means of separation. Here 
and there a good many individual genera may be picked out capable of 
the most accurate definition ; but genera like these are in the minority, 
and most of the remainder present several apparent alliances, from which 
we are at a loss to choose that which is nearest. our of the six groups 
of Mr. Sclater’s “ Laminiplantar” Oscines seem to pass almost imperceptibly 
into one another. We may take examples in which what we may call the 
Thrush-form, the Tree-creeper-form, the Finch-form, or the Crow-form is 
pushed to the most extreme point of differentiation, but we shall find that 
between the outposts thus established there exists a regular chain of 
intermediate stations so intimately connected that no precise lines of 
demarcation can be drawn cutting off one from the other. 
Still one thing is possible. Hard though it be to find definitions for 
the several groups of Oscines, whether we make them more or fewer, it is 
by no means so hard, if we go the right way to work, to determine which 
of them is the highest, and, possibly, which of them is the lowest. It has 
already been shewn (page 72) how, by a woeful want of the logical appre- 
hension of facts, the T’wrdide came to be accounted the highest, and the 
position accorded to them has been generally acquiesced in by those who 
have followed in the footsteps of Keyserling and Blasius, of Prof. Cabanis 
and of Sundevall. Now the order thus prescribed seems to be almost the 
very reverse of that which the doctrine of Evolution requires, and, so far 
from the Turdidx being at the head of the Oscines, they are among its 
lower members. There is no doubt whatever as to the intimate relation- 
ship of the Thrushes (Zurdidx) to the Chats (Sawicoline), for that is 
admitted by nearly every systematizer. Now most authorities on classifica- 
tion are agreed in associating with the latter group the Birds of the 
Australian genus Petreca and its allies (WHEATEAR, pp. 1085, 1036)— 
the so-called “ Robins” of the English-speaking part of the great southern 
communities. But it so happens that, from the inferior type of the osteo- 
logical characters of this very group of Birds, the late Prof. Parker called 
them (Trans. Zool. Soc. v. p. 152) “Struthious Warblers.” Now if the 
Petraca-group be, as most allow, allied to the Sasicoline, they must also 
