The group is a very large one, and it is probable that there are at least 300,000 different kinds of insects already known, while the total number of species now existing is estimated by different entomologists as from two to ten millions. It is, therefore, no exaggeration to say that every word of our brief account of the Insects represents from ten to twenty known species at least. The other classes of the group are also very numerous. Our account must necessarily be very short; the characters of the principal classes of the Jointed Animals are referred to in their places.
Crabs, Lobsters, Shrimps, Wood-lice, Barnacles, etc.
Photo by W. P. Dando, F.Z.S., Regent's Park.
A PAIR OF BARNACLES.
The larger size of this photograph exhibits more structural details than the last.
Jointed animals are generally provided with one pair of long jointed organs, called "antennæ," a naturalised word derived from the Latin, in which language antenna means a sail-yard. They are often called "feelers," and usually fulfil this function at least; but they are also frequently organs of smell, and sometimes probably of hearing and other senses. One peculiarity of the Crab and Lobster group is that they are generally furnished with two pairs instead of one pair of these organs.
Photo by W. P. Dando, F.Z.S.] [Regent's Park.
ACORN-BARNACLE.