Chet Cs Ee NOEs. 
In the following notes I have given my reasons for the alterations I 
have thought necessary to make ; as, however, most of them refer to the 
much vexed question of what constitutes a species, and what a variety, 
a short prefatory statement of my views on this subject is, I think, 
necessary. 
Accepting, as I do with confidence, the theory of the gradual devel- 
opment of species, by small progressive variations from previously 
existing forms, it appears to me that when seeking to ascertain whether 
a certain variation is sufficient to characterise a new species, we are, in 
truth, seeking to ascertain how long this variation has been in existence, 
for until it had existed for a considerable period it could not have 
deviated sufficiently from the parent form to entitle it to constitute a 
distinct species, and it is also highly improbable that a variation would 
continue constant for a great length of time without further progression 
in the same direction, for constancy implies utility, and a useful variation 
must be a progressive one. 
What, then, may be considered as characterising age in variations ? 
1. Constancy, for it proves a long line of similar ancestors. 
2. Absence of intermediate varieties. 
3. The principal variations being accompanied by other minor, 
but generally constant variations. 
4, The extent of the variation, provided it is constant. 
5. The abundance of individuals possessing the variation, and 
their wide distribution, except in those cases where the 
modifications are adapted for local or exceptional circum- 
stances, and where impassable barriers to diffusion exist. 
In my opinion, therefore, before a variety can be considered as suffi- 
ciently distinct to entitle it to rank as a separate species, its distinguish- 
ing character must be constant, not connected by intermediate stages 
