264 MR. J. WATSON ON THE PLUMULES OR 



Mr. Bates, in his ' Naturalist on the River Amazons/ 

 vi. pp. 251 &c. (1863), devotes some pages to show that 

 many species of this genus have had a common origin, 

 proving the " manufacture of new species in nature.^^ He 

 takes "Melpomene, abundant in Guiana, Venezuela, and 

 some parts of New Granada,"*^ as the original species, and 

 argues that Thelxiope, "ranging 2000 miles from east 

 to west, from the mouth of the Amazons to the eastern 

 slopes of the Andes," is merely a local modification ; and 

 yet he says that "if local conditions, acting directly on 

 individuals, had originally produced this race or species, 

 they certainly would have caused much modification of it 

 in dififerent parts of this region ; for the Upper Amazons 

 country differs greatly from the district near the Atlantic 

 in climate, sequence of seasons, soil, forest-clothing, peri- 

 odical inundations, and so forth.^' He then proceeds to 

 contend " that there is some more subtle agency at work 

 in the segregation of a race than the direct operation of 

 external conditions,'^ and that the principle of natural 

 selection, as lately propounded by Darwin, " seems to offer 

 an intelligible explanation of the facts.'' 



The plumules, however, enable an observer to detect 

 without doubt the species : if those taken from any number 

 of specimens of the species Melpomene, Thelxiope, Acede, 

 and Vesta are examined, each can be named; but mere 

 varieties of each species will exhibit the same plumule, as 

 in the case of Thelxiope and Aglaope. Surely, if the Dar- 

 winian theory were true, that a change is constantly in 

 progress, we ought to find plumules of an undecided form 

 in some specimens, partaking of and hovering between 

 the characteristics of their supposed ancestors. With all 

 deference to Mr. Bates, whose opportunities of observa- 

 tion have been great, I cannot but regard his theory as 

 improbable and far-fetched. Why should Thelxiope have 

 descended from Melpomene rather than the latter from 



