ON THE STUDY OF ZOOLOGY 359 ' 



shrimp, for example, however different, are yet so like 

 lobsters, that a child would group them as of the lobster 

 kind, in contradistinction to snails and slugs ; and these 

 last again would form a kind by themselves, in contra- 

 distinction to cows, horses, and sheep, the cattle kind. 



But this spontaneous grouping into " kinds " is the 

 first essay of the human mind at classification, or the calling 

 by a common name of those things that are alike, and the 

 arranging them in such a manner as best to Suggest the sum 

 of their likenesses and unlikenesses to other things. 



Those kinds which include no other subdivisions than the 

 sexes, or various breeds, are called, in technical language, 

 species. The English lobster is a species, our cray fish 

 is another, our prawn is another. In other countries, 

 however, there are lobsters, cray fish, and prawns, very 

 like ours, and yet presenting sufficient differences to 

 deserve distinction. Naturalists, therefore, express this 

 resemblance and this diversity by grouping them as distinct 

 species of the same " genus." But the lobster and the cray 

 fish, though belonging to distinct genera, have many 

 features in common, and hence are grouped together in an 

 assemblage which is called a family. More distant resem- 

 blances connect the lobster with the prawn and the crab, 

 which are expressed by putting all these into the same order. 

 Again, more remote, but still very definite, resemblances 

 unite the lobster with the woodlouse, the king crab, the 

 water flea, and the barnacle, and separate them from all 

 other animals ; whence they collectively constitute the 

 larger group, or class, Crustacea. But the Crustacea 

 exhibit many peculiar features in common with insects, 

 spiders, and centipedes, so that these are grouped into 

 the still larger assemblage or " province " Articulata ; and, 

 finally, the relations which these have to worms and other 

 lower animals, are expressed by combining the whole vast 

 aggregate into the sub-kingdom of Annulosa. 



If I had worked my way from a sponge instead of a 

 lobster, I should have found it associated, by like ties, with 

 a great number of other animals into the sub-kingdom 

 Protozoa ; if I had selected a fresh-water polype or a coral, 

 the members of what naturalists term the sub-kingdom 

 Coslenterata would have grouped themselves around my 

 type ; had a snail been chosen, the inhabitants of all 

 univalve and bivalve, land and water, shells, the lamp 

 shells, the squids, and the sea-mat would have gradually 



