10 



existing are contained, and very fairly illustrate the rule I am 

 dealing with. 



The group is an interesting one, and probably originated on 

 the south side of the equator. All the species except the Ostrich 

 are still found in the southern hemisphere only, but the con- 

 tinuity of the African continent has enabled the Ostrich to pass 

 the equator, the conditions being also favourable to its existence 

 in North Africa. 



The Rheas have not, however, passed the equator in South 

 America, the Pampas not extending sufficiently far north. 



The Humming Birds, although very elegant and gorgeously 

 coloured birds, are lowly organized as birds ; their habits are 

 almost the same as those of insects, and in some points of struc- 

 ture they assimilate more to the reptiles than other birds. 



It is almost unnecessary to add that, of all birds, they are by 

 far the smallest, some species not being more than two and a half 

 inches in length. 



The Sunbirds of the Old World are nearly as small as the 

 Humming Birds, and but a little higher in organization. 



The different divisions of the Annulosa appear to confirm the 

 rule that size is correlated with high development. 



Amongst the Crustaceans the Stalk-eyed are larger than the 

 Sessile-eyed, and in the former the liighly developed Crabs and 

 Lobsters are larger than the more lowly developed Prawns, Shrimps, 

 and Squills. 



The time at my disposal will not allow me to draw your atten- 

 tion to many of the groups of Insects and other divisions of the 

 Annulosa. 



The highly developed Lepidoptera attain a larger size, in the 

 typical families, than the lower Neuroptera and Homoptera. 



Amongst the Lepidoptera Rhopalocera, the true Papillionidae, 

 placed at the head of the order, are also of the largest average size ; 

 and the largest of the true Butterflies are also the largest of the 

 Lepidoptera, in the expanse of wing, and inferior in the bulk of 

 their bodies only to some of the Sphingidse and Bombycidte, 

 which are placed at the head of the Lepidoptera Heterocera. 



The aberrant groups, such as the Tortricidse and Tineinte, are 

 of very small size — none large, and thousands of species only a 

 few lines in length, the alar expansion of the smaller species being 

 under three lines, and the length of the body not more than one 

 line. 



