66 APPENDIX : NO. XLIV. 
of various branches from one common stock ;—it will be admitted 
we must be in considerable difficulty in adapting the word species 
to our new ideas, and supposing this to be done, great obscurity 
must still remain respecting individual cases. Without, however, 
discussing the question,—Wahat is a species ? it appears to be pretty - 
generally agreed that if no obvious structural difference can be 
shown to exist, beyond what may be due to age, sex, or season, 
there is no presumption of a distinction of species, unless at all 
events there can be found some marked variations in the actions of 
life, and especially a constant restriction in interbreeding. It 
follows, if the rule is stated correctly, that Mr. Newton must not 
throw the onus probandi on those who do not believe the Ringed 
Guillemot to be a distinct species, at least if this assertion be not 
denied, namely, that there has not been proved any appreciable 
structural difference between it and the Common Guillemot. For a 
constant restriction in interbreeding has not been shown, and the 
only variation in the actions of life hinted at has been the occupa- 
tion of particular shelves of the rock. But that peculiarity might 
be owing to age, for it is probable that of all gregarious species, as 
certainly of Rooks, the old birds take the best places for themselves, 
leaving the outskirts to the younger members of the community. 
Even then admitting the fact of the segregation, I think no case is 
made out for those who would subdivide the species of the Common 
Guillemot. But I do not admit the supposed fact as a general 
truth. Even if the information given to Mr. Proctor in Iceland 
be correct (and Mr. Newton’s observations in the Farn Islands 
tended to confirm it), it is certain in this country, and in the Faroe 
Islands, the birds lay their eggs promiscuously. In the year 1849 
I paid particular attention to this subject. First, I saw a large 
assemblage of Guillemots on April 22 (a sunshiny day), upon the 
flat summit of the rock called the Kleat, at Holborn Head, in 
Caithness. There were several hundreds of them standing together 
on the guano-covered platform of that lofty stack. They were not 
more than forty or fifty yards from me, and with a glass I could see_ 
them as well as if they had been in my hand. Perhaps every sixth 
bird amongst them had the white margin to the eyes, and the white 
line extending from it. They were courtesying and bowing to each 
other, without any reference, so far as J could see, to the presence 
or absence of the facial peculiarity ; and as I carefully watched this 
match-making party for some time, had they shown any marked 
preferences, I could hardly have failed to observe it. At the 
beginning of June, in the same year, I became familiar with the 
Guillemots on the cliffs of the island of Handa, off the coast of 
Sutherland, on which they are in myriads. I was not satisfied with 
looking at them from above, but with the help of a rope I went 
amongst them in every part of the rocks on three or four days. 
The Ringed ones seemed rather less numerous than in Caithness ; 
they were scattered amongst the others, neither often mixing with 
the Razor-bills on the upper shelves, nor confining themselves to the 
