MONSTROSITIES 319 



that of the Great Hornbill. In some the crest on the upper 

 mandible is small. It is quite conceivable that the crest enlarged 

 gradually up to a certain point, and that by a sudden monstrous 

 enlargement it reached the size we see on the mandible of the Great 

 Hornbill. 



Then there is Toccus elegans and Toccus Moniieri^ which have 

 enormous bills like those of the Great Hornbill, but without a trace 

 of the monstrous crest. The Condor has a crest on its upper man- 

 dible not unlike that of the Hornbills. 



Mr. F. W. Headley ^ writes : ' The Hornbills are a puzzle. The 

 extreme shortness of the hand bones, a ridiculous anticlimax 

 following upon so grand an ulna and so portentous a humerus, 

 might suggest that they were once better flyers, and that the wing 

 is slowly undergoing reduction. But the mountainous beak seems 

 to show that colossal bones are an ancient heritage of the family, 

 and that even feeble flight might have been difficult had they not 

 become hollow.' 



From this it would seem that Mr. Headley would suggest that 

 the immense beak of the Hornbill was inherited from some ancestor 

 with a colossal body, but this does not touch the origin of the 

 immense crest, seemingly useless, on the upper mandible of the 

 Great Hornbill. As these birds are frugivorous, this colossal bill 

 would seem to be rather a nuisance among the branches of trees. 



There can be little doubt that in the course of evolution an 

 occasional monstrosity, as a sudden large variation, would facilitate 

 the interpretation of such vagaries in nature and of many a diffi- 

 cult problem in evolution.^ 



^Proc. Zool. Soc. 1865, p. 86. 



^ 'The Air Sacs and Hollow Bones of Birds,' Natural Science, No. 21, vol. iii. 

 p. 352, Nov. 7, 1893. 



'^ The extinct Pterodactyls had immense bills, not unlike those of the Hornbills, and 

 among them we may yet find this ancestry of the massive bill of the Hornbills ! 



