SCIENTIFIC CULTIVATION OF BRITISH BEES. 147 
More extensive collecting has also shown that some of 
his species are merely varieties of others, which have 
thus been brought to their authentic type. This also 
could only be proved by experience, for it is remarkable 
how very Protean some species are, whilst others are 
almost rigidly unchangeable. Evidently there does exist 
a line of demarcation between distinct species, which 
only requires to he diligently sought to be found, 
obscure as it may appear to be, but which the insects 
themselves obey, for however closely species may some¬ 
times approximate, yet I do not believe, as I have before 
expressed, that they ever permanently coalesce, and that 
they are always as distinctly separate as are asymptotes. 
As Mr. Kirby’s work is in few hands, or perhaps not 
readily accessible, I will give here a summary outline of 
it, with the names of the genera with which his families 
coincide. 
In this work he established only two named genera— 
Melitta and Apis. 
His genus Melitta, which is equivalent to the subse¬ 
quent subfamily Andrenidce, he divides into two sections, 
* and * *, the first containing two families, a and b, (these 
we call genera, and they are now named Colletes and 
Prosopis) ; the second section * * contains three fami¬ 
lies, a, b, c, ( a , is Sphecodes, b, Halictus, and c comprises 
our three genera, Andrena, Cilissa, and Dasypoda.) 
His genus Apis he also divides into tw 7 o sections, * 
and * * ,• the first is subdivided into two families, a and 
b (our genera Panurgus and Nomada ) ; and the second 
is divided into five subsections, a, b, c, d, e; a and b 
constitute families (our genera Melecta and Epeolus ). 
The subsection c is divided into two parts, 1 and 2, 
the first containing the two divisions a and {3, each 
l 2* 
