1878.] Variations in the Nests of the same Species of Birds. 35 
bird at least had been compelled to lay her eggs, and then must 
leave them behind. And this pretty treasure on my table is one 
of them. Interesting, was it said? Nay, is it not historic, a me- 
mento of this remarkable exodus of the night herons from their 
almost romantic heronry at Three-mile Run, New Jersey. Do 
you ask, “ Did they hold together as in a well-ordered retreat ? 
And did they establish a heronry elsewhere? Or did the dis- 
pirited community dissolve itself into the isolation of single pairs? 
And finally, where did they go?” Well, just these are the ques- 
tions which we are aching to find out. Meanwhile, let this much 
go on the record, of the time, circumstance, and spirit of the exodus 
of this ancient colony of birds. 
20: 
VARIATIONS IN THE NESTS OF THE SAME SPECIES 
OF BIRDS. 
BY DR. T. M. BREWER. 
N the present brief paper I propose to deal more with facts than 
with theories. I leave to others to make such deductions there- 
from as may suggest themselves. When one cannot, to his own 
satisfaction, point out the reasons that can fully account for indis- 
putable facts, it seems to be the safer course to be content with 
only taking cognizance of natural phenomena, just as they im- 
press our senses. The legitimate scope of the naturalist is first 
correctly to describe isolated facts as they present themselves. To 
seek to investigate the laws that unite these, though always 
tempting, is not always safe. The homely advice: “ Never to 
prophesy unless you know,” is applicable to the case. There is 
no worse bondage to the student of nature than to be a slave to 
theory. The danger of a “little learning ” is of its leading to un- 
warrantable deductions, and then the temptation to color facts to 
suit preconceived opinions may become one of the besetting 
weaknesses of our human nature, against which it behooves nat- 
_uralists especially to struggle manfully. 
From time immemorial the theory has been prevalent, and 
generally accepted, that the constructions of all animals, man 
= excepted, are the inevitable results of a faculty called instinct. 
_ On the other hand it is claimed that all the constructions made by _ 
man are due to another faculty known as reason. To this I am 
