496 INSTINCT OF INSECTS. 
You will not doubt my allowing the. appositeness of 
this question, when I frankly tell you, that so strikingly 
do many of the preceding facts seem at first view the ef- 
fect of reason, that in my original sketch of the letter you 
are now reading, I had arranged them as instances of 
this faculty. But mature consideration has convinced 
me (though I confess the subject has great difficulties) 
that this view was fallacious; and that though some cir- 
cumstances connected with these facts may, as I shall 
hereafter show, be referable to reason, the facts them- 
selves can only be consistently explained by regarding 
them as I have here done, as examples of variations of 
particular instincts :—and this on two accounts. 
In the first place, these variations, however singular, 
are limited in their extent: all bees are, and have always 
been, able to avail themselves of a certain number, but 
not to increase that number. Bees cemented their combs 
when becoming heavy, to the top of the hive, with mitys, in 
the time of Aristotle and Pliny as they do now; and there is 
every reason to believe that then, as now, they occasionally 
varied their procedures, by securing them with wax or 
with propolis only, either added to the upper range of 
cells, or disposed in braces and ties to the adjoming 
combs. But if in thus proceeding they were guided by 
reason, why not under certain circumstances adopt other 
modes of strengthening their combs? Why not, when 
wax and propolis are scarce, employ mud, which they 
might see the martin avail herself of so successfully? Or 
why should it not come into the head of some hoary 
denizen of the hive, that a little of the mortar with which 
his careful master plasters the crevices between his habi- 
tation and its stand, might answer the end of mitys? 
