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 Coraciidce and the Alcedinidce in opposition 

 to other groups may be expressed by the term Halcyones ; the frequent 

 occurrence of blue non-metallic colour in these birds favours the 

 acceptance of such a term. 



The Striges verge towards the plagiocoelous type, but all their 

 affinities rest with the Coraciidoe and Cafirimulgidse combined. 

 These three families possess long caeca ; the Alcedinidai, Cypselidse, 

 and Trocliilidae have lost them, the first of these because of their 

 piscivorous and cancrivorous habits. 



The Caprimulgidce, Cypselidce, and Trochilidee agree very much 

 with each otlier. 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 Trochilidse differ in the 

 possession of a crop. Tlie Cypselidce and Caprimulgidce are somewhat 

 more closely related to each other, and the latter (including Podargus) 

 turn towards the Owls. The Cypselidse 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 Trogonidce stand on a lower level than the Cypselidse, 

 Trochilidse, and Coliidae, on the same level as the Caprimulgidae and 

 Coraciidse, 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 csDca like the 

 Coraciidse, Caprimulgidae, and Striges, whilst all the other Corac- 

 ornithes inside the isoccelous circle have lost them, or have only 

 fuDctionless remnants of them. 



We cannot divide the whole host of Coracornithes into Meno- and 

 Lipotyplila, because the loss of the cseca does not indicate relation- 

 ship, and has been produced independently by the absence or scarcity 

 of cellulose orchitinous 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 left in 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- 

 diseidse, &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. 



