It may be doubted that there are many other animals which have played so important a part in the history of the world as have these lowly organized creatures.

The willing horse is always overworked.

It is well-known that those who have charge of young infants, that it is difficult to feel sure when certain movements about their mouths are really expressive; that is when they really smile. Hence I carefully watched my own infants. One of them at the age of forty-five days, and being in a happy frame of mind, smiled... I observed the same thing on the following day: but on the third day the child was not quite well and there was no trace of a smile, and this renders it probable that the previous smiles were real.

One day, on tearing off some old bark, I saw two rare beetles, and seized one in each hand. Then I saw a third and new kind, which I could not bear to lose, so I popped the one which I held in my right hand into my mouth. Alas! it ejected some intensely acrid fluid, which burnt my tongue so that I was forced to spit the beetle out, which was lost, as was the third one.

Animals manifestly enjoy excitement, and suffer from annul and may exhibit curiosity.

Intelligence is based on how efficient a species became at doing the things they need to survive.

May we not suspect that the vague but very real fears of children, which are quite independent of experience, are the inherited effects of real dangers and abject superstitions during ancient savage times?