DIGESTIVE SYSTEM 147 



The Pelargi are often classed with the Herodii, but these two 

 Families differ from each other in almost every point of primary 

 importance. 



There are also certain resemblances between the Pelargi and the 

 Accipitres, the chief connexion is formed by the telogyrous character, 

 the mode in which additional loops of the lengthened gut are stowed 

 away, and the tendency to convert some or one of the principal 

 loops into regular spirals. Among the Accipitres, the Old- World 

 Vultures especially exhibit striking Ciconiine similarities. As 

 regards the Cathartidas, I have to deplore want of material. 



The Psittaci are distinctly telogyrous ; all their five principal 

 loops are closed and alternating ; this, with the presence of a crop, 

 and the absence of functional caeca, are features which occur again 

 together only in the Accipitres. The absolutely vegetable food of 

 the Parrots would sufficiently account for the differences which exist 

 between them and the entirely zoophagous Accipitres. However, 

 this indication of a possible relationship between the Birds-of-Prey 

 and Parrots is as little binding or satisfactory as other suggestions 

 based upon other organic systems. 



Of the Coccyges the Cuculidse possess four intestinal loops, of 

 which the first and second are right-handed. The loops are on the 

 whole orthocoelous, but the apices of the two middle ones are often 

 turned up, or the second loop is plagiocoelous. Moreover, they 

 possess fully-developed caeca. In all these respects they resemble 

 to a great extent the Gallinse; and this hint is considerably 

 strengthened by Opisthocomus, which is, barring special features, 

 exactly intermediate between the Cuculidae and the Gallinaz. The 

 Mus&phagidx seem to possess but three loops, the original second 

 loop having been suppressed in connexion with the frugivorous 

 habits of these birds. The isocoelous feature of the Musophagidse is 

 therefore reduced to a secondarily acquired one, and to a case of 

 convergence towards the typically isocoelous birds. 



The Pici {Picidm, Capitonidse, and Rhamphastidse) difi"er, like tho 

 Epopes {Bucerotidm, and Upupidse), from all the remaining birds in 

 the alternating position of their four loops, which in the frugivorous 

 Bliamphastidx, as well as in the extremely short-gutted genus Upupa, 

 are reduced to three by the suppression of the original second loop. 

 Xantholsema, one of the Capitonidae, has this second loop still indicated. 

 The total absence of caeca in all these birds is a coincidence, while 

 there are no obvious characters, besides the anticoelous convolutions, 

 which point to a close relationship between the Pici and the Epopes. 



The remaining birds are all isocoelous. Of them the Coraciidse 

 stand nearest to the hypothetical ancestral or central stock, because 

 they are the most generalized group, from which all others can be 

 derived. The Alcedinidse, which have reached a truly mesogyrous 

 formation, started in one direction from or out of the Coraciidse. 



