38 
Mr. Robert Collett on 
All these transition-forms (possibly with but one solitary 
exception) were males; also the last-mentioned variety. 
The question as to when and in what condition these 
specimens of L. excubitor, either with no or with an imper¬ 
fectly developed basal spot on the secondaries, are found to 
occur, can hardly at present be satisfactorily settled. 
First of all, it is evident that the presence or absence of 
the basal spot on the secondaries cannot be dependent on 
age, since both single-spotted and double-spotted individuals 
belonging to the same brood occur even in the nesting- 
plumage. 
Furthermore, should the varying colour of the secondaries 
arise from a gradual change, and the imperfectly developed 
basal spot in the course of the winter and spring become a 
perfect one (as with the primaries of Plectrophanes nivalis , 
which pass, without moulting, from brownish grey to white), 
a change in this respect would necessarily take place with 
such individuals also as exhibit a very small or no basal spot 
whatever on the secondaries, and not in transition-specimens 
alone. 
Thirdly, sex exerts no decided influence, although single- 
spotted individuals are more frequently found to be females 
than males. 
Finally, as regards the latitude, it is generally admitted 
that the single-spotted form (comprising also less typical or 
transition individuals) belongs to the northern or north¬ 
eastern tracts of the Palsearctic Region, whereas the typical 
L. excubitor inhabits Western and Central Europe. Mean¬ 
while we must bear in mind that every year, now that 
attention has been drawn to the subject, more or less typical 
specimens of the single-spotted form (. L . major , Cab.) are 
shown to occur regularly or commonly in most tracts along 
with the normal L. excubitor , extending to Austria and 
Hungary; while, as stated above, the true L. excubitor has 
also been found to inhabit and breed in the Arctic regions 
(Finmark). Other examples are recorded from Archangel 
(Meves), from the Ob (Finsch); and their number will 
assuredly increase every year. 
