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of a small spider, scarce the eighth of an inch long, found in coal 
mines. “In its natural state this spider is met with in meadows 
about the time of hay-harvest, and is only known as a solitary 
wanderer, making ~o web of any kind, further than a few scattered 
lines. In the coalpits, into which they are supposed to have been 
carried down originally by accident with the provender for the 
horses, they become gregarious and live in large colonies, 
constructing sheets of web of vast size. An observer is recorded 
to have seen one 30 feet long by four and a half feet wide, 
hanging from about the middle of the roof.” This is a note- 
worthy incident. 
One might almost imagine that these little spiders,—living quite 
independentof each other up to the time of their being carried down 
into the pit,—had held consultation, and come to an agreement, 
as to how they should meet so unexpected an emergency and 
carry on their lives in future. And what must have been the 
potentiality of their minute spinnerets, never before brought into 
use in this way, to render them equal to the production of such a 
web! It seems to hint to us what we may all do, if we only set 
ourselves to any required task in good earnest. 
The fact which lies at the bottom of all these variations of 
structure and instincts such as I have been speaking of, is the 
readiness of nature ‘“‘to grow to the situation,” as I think Dr. 
Carpenter somewhere terms it, 7.¢., gradually to adapt itself to 
any change in the surrounding circumstances of animals that is 
not absolutely fatal to them ; as also, on the other hand, to any 
ingrowth of habits in the animals themselves, foreign to what is 
usual in their congeners or near allies. 
If you doubt this statement only look around and see what is 
going on about you. The busy world we live in speaks every 
where to the existence of such changes, and often indicates in 
what way they are occasioned. See the effects of use and disuse 
on the organs of the body. Our own habits are mostly acquired 
in the same way as those of animals. Watch the nimbly-moving 
