118 Transactions.—Zoology. 
Celebes, the Navigators, the Caroline Islands, New Caledonia, the Philippine 
Islands, and New Zealand, are referable to one and the same species, we are 
bound, it seems to me, to adopt the older name of R. philippensis, Linn. 
(Syst. Nat., i, p. 263). 
Hydrochelidon leucoptera, Temm. 
I believe Capt. Hutton is right in his identification of Mr. Monro’s 
specimen in the Colonial Museum, although Dr. Finsch thinks he has 
confounded it with H. hybrida, Pall. Almost immediately after my arrival 
in England I had an opportunity of examining a fine series of these birds in 
the collection of Mr. Howard Saunders, and having at that time a very 
distinct recollection of the New Zealand specimens, I satisfied myself that they 
were the same. 
Eudyptes pachyrhynchus, Gray. 
I have treated this in my work as a synonym of Zudyptes chrysocomus. 
Apteryx mantelli, Bartl. 
Dr. Finsch states that “after careful and repeated examination” of several 
specimens from both islands, he is unable to admit Apteryx mantelli (of the 
North Island) to the rank of a distinct species ; but he proposes to distinguish 
it from the South Island form as “ Apteryx australis var. mantelli, Bartl,” 
This opens up again the old quæstio vexata, ** what is a species?” 
The amount of difference necessary to constitute a “species,” in the 
generally accepted sense, is not capable of definition, and must ever remain, to 
a, certain extent, a matter of opinion with each individual naturalist. 
I have already stated fully my reasons for keeping the two forms 
specifically distinct (“Birds of New Zealand,” pp. 366—367) ; and it is sufficient 
for my argument that Dr. Finsch recognizes constant characters in the North 
Island bird of a kind to distinguish it as a permanent “ variety.” 
I may add that I had the satisfaction of submitting good specimens of 
Apteryx australis and Ap. mantelli to Professor Newton, Dr. Sclater, 
Mr. Salvin, and Mr. Sharpe, all of whom were decidedly of opinion that the 
characters relied on were of sufficient importance to warrant the separation of 
the species. 
