XXVili MEMOIR. 
are clothed with minute feathers or scales, coloured in regular patterns, which 
vary in accordance with the slightest change in the conditions to which the 
species are exposed. It may be said, therefore, that on these expanded 
membranes Nature writes, as on a tablet, the story of the modifications of 
species, so truly do all changes of the organisation register themselves 
thereon. Moreover, the same colour-patterns of the wings generally show, 
with great regularity, the degrees of blood-relationship of the species. As 
the laws of nature must be the same for all beings, the conclusions furnished 
by this group of insects must be applicable to the whole organic world; there- 
fore, the study of butterflies—creatures selected as the types of airiness and 
frivolity—instead of being despised, will some day be valued as one of the 
most important branches of biological science.” * 
Ega was then an alderman’s paradise, the staple food being 
turtles, costing about ninepence each. But Bates grew so sick of 
this diet that he often preferred to remain hungry. For two years 
he did not taste wheaten bread, using tapioca soaked in coffee as 
the best substitute. Such poor living, with other drawbacks and 
privations, brought about physical prostration and ultimate collapse. 
Steamers were introduced on the Upper Amazons in 1853, and 
in November 1856 Bates availed himself of this improved means of 
transport. He embarked in the Zadatinga for the river Tunantins, 
and thence took a trading vessel to Fonte Boa, “the head-quarters 
of mosquitoes,” where he stayed till the following January. From 
this point he re-embarked in the steamer and landed at St. Paulo, 
four hundred miles from Ega by water, and one thousand eight 
hundred miles from Para. There, where “ five years would not have 
been sufficient to exhaust the treasures of its neighbourhood in 
zoology and botany,” he remained five months, when severe illness 
compelled him to abandon a cherished plan of proceeding to the 
very foot of the Andes. He returned invalided to Ega, still hoping 
“to gather the yet unseen treasures of the marvellous countries 
lying between Tabatinga and the slopes” of the great range. But 
his general health remained too weak to justify any further work 
of exploration, and on February 3rd, 1859, he left Ega, ev route for 
England, having spent eleven of the best years of his life within 
four degrees of the equator, to the permanent enrichment of our 
knowledge of one of the most interesting regions of the globe. 
In an approximative enumeration of the number of species of 
the various classes obtained between 1848 and 1859 given in the 
preface to the Travels, the total is shown to reach 14,712, of which 
insects number 14,000, and mammals 52. The very small number 
* Infra, pp- 351-353- 
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