REMARKS SUGGESTED BY THE STUDY OF THE EPHEMERID. 63 

to Asia ; and the genus Cloéon is found in these continents as well 
as in Africa. Of 180 species, only four have been found in more 
than one continent, and none of these four in more than two con- 
tinents; and even in these widely-distributed species the areas 
inhabited by each in any one continent are of limited extent ; as, for 
instance, in the case of Baetis binoculatus, which has been found in 
temperate and arctic Europe and the Hudson’s Bay Territory of 
America. In respect to their geographical distribution, therefore, 
they accord with the general law of the distribution of animals, 
viz: That existing species are, as a rule, confined to limited areas, 
each area being known by its characteristic fauna, whilst the allied 
species of several areas constitute a genus. 
Seeing that the abortive mouth of these insects in the imago 
state necessitates a very brief span of aérial life, usually but a few 
hours, we are led to inquire into the object of their final trans- 
formation. Could they not have provided for the perpetuation of 
the species without leaving the water, in which thé female might 
deposit her eggs more securely at the bottom than by dropping 
them on the surface, as is her custom? ‘The chief purpose pro- 
bably of the wings of those insects that pass their lives before 
maturity in the water was originally to find fresh breeding grounds 
in which to deposit their eggs ; as otherwise certain waters would 
have become overstocked, their food exhausted, and the perpetua- 
tion of the species unprovided for. As the waters in which they 
live are often isolated, and never intercommunicate to any great 
extent, the ubiquity of the family could be secured only by the 
acquisition of wings. The winged state of the Ephemeridz is 
thus accounted for to some extent. But when we consider the 
beauty of their variegated colours, especially of the female, which 
could be produced only by reflected light in the air, and how much 
such adornment may contribute to the development of the sexual 
instinct of the more sombre male; and when we realize from 
observation of their mazy dances in the sunlight, as they hover 
with ceaseless motion above the water from which they have just 
emerged, the amount of physical enjoyment that may be comprised 
in their novel mode of life—an enjoyment which nature so bounti- 
fully provides for all who obey her laws,—if we could analyze their 
sensations and translate their significance into language, we might, 
perhaps, arrive at the conclusion that these little creatures share 
the opinion of certain ambitious spirits of the human family, that 
‘One crowded hour of glorious life 
Is worth a century of ease.” 
In reference to the antiquity of these insects, we meet with 
various statements from time to time as to their fossil remains 
having been found in the Palzeozoic rocks. Sir Charles Lyell 


