1889. ] CONVOLUTIONS IN BIRDS. 315 
handed spiral in its second loop, whilst the fourth loop is long, and 
in the more piscivorous members widely open and irregularly placed. 
The affinity between the Coraciide and the Alcedinide in opposition 
to other groups may be expressed by the term Halcyones ; the frequent 
occurrence oi blue non-metallic colour in these birds favours the 
acceptance of such a term. 
The Striges verge towards the plagioccelous type, but all their 
affinities rest with the Coraciidee and Caprimulgide combined. 
These three families possess long czeca; the Alcedinide, Cypselide, 
and Trochilidee have lost them, the first of these because of their 
piscivorous and cancrivorous habits. 
The Caprimulgide, Cypselide, and Trochilide agree very much 
with each other. They are, however, all of equivalent rank. They 
all have only three intestinal loops, which are short, in agreement with 
their principally insectivorous habits. The Trochilide differ in the 
possession of acrop. The Cypselide and Caprimulgide are somewhat 
more closely related to each other, and the latter (including Podargus) 
turn towards the Owls. The Cypselide are sometimes supposed to 
be somewhat nearly allied to the Passeres. Their alimentary system 
does not altogether favour such a view; but perhaps the ancestors 
of Colius once filled this gap, leaving their sole recent descendant 
now in a solitary position. 
The TYrogonide stand on a lower level than the Cypselide, 
Trochilidz, and Coliidze, on the same level as the Caprimulgidz and 
Coraciide, and connect them all with each other. How much of 
this is mere coincidence, I am unable to decide, owing to want of 
material. The Trogons still possess well-developed cca like the 
Coraciidze, Caprimulgide, and Striges, whilst all the other Corac- 
ornithes inside the isoccelous circle have lost them, or have only 
functionless remnants of them. 
We cannot divide the whole host of Coracornithes into Meno- and 
Lipotyphla, because the loss of the czeca does not indicate relation- 
ship, and has been produced independently by the absence or scarcity 
of cellulose or chitinous substances in the food taken. 
The Passeres are a very uniform group, equivalent to the Halcy- 
ones, Pici, Striges, &c. Their roots lie in the anticcelous assemblage, 
nearer to the right than to the leftin the diagram. They all possess 
only three loops, without indications of more; the second and third 
are left-handed ; the second becomes a left-handed spiral, the turns 
of which depend upon the length of the gut; the third loop is 
always open, and invariably encloses the duodenum between its 
descending and ascending branches, the latter branch being situated 
on the ventral and left side of the descending branch of the duo- 
denum. This arrangement is invariably the same, even in the 
Mesomyodians, and in such otherwise aberrant forms as Rupicola and 
Pitta. ‘There is a special line which leads from the Laniine forms 
through the Austrocoraces (Gymnorhina, Graucalus, Strepera, Para- 
diseidze, &c.) into the Coraces proper, which latter have produced 
some special modifications of the intestinal convolutions, and may 
be looked upon as the last and highest blossom of the Avian tree. 
