BY W. T. CALMAN, D.Sc.   WITH THIRTY-TWO PLATES AND EIGHTY-FIVE FIGURES METHUEN & CO. LTD. 36 ESSEX STREET W.C. LONDON First Published in 1911...

This sketch of the Natural History of the Crustacea deals chiefly with their habits and modes of life, and attempts to provide, for readers unfamiliar with the technicalities of Zoology, an account of some of the more important scientific problems suggested by a study of the living animals in relation to their environment. I am indebted to the Trustees of the British Museum for leave to reproduce certain figures prepared for the "Guide to the Crustacea, Arachnida, Onychophora, and Myriopoda exhi

Everyone has some acquaintance with the animals that are grouped by naturalists under the name Crustacea. The edible Crabs, Lobsters, Prawns, and Shrimps, are at least superficially familiar, either as brought to the table or as displayed in the fishmonger's, and the most unobservant of seaside visitors must have had his attention attracted by living specimens of some of the more obtrusive species, such as the common Shore Crab. Many, however, will be surprised to learn that the Barnacles coatin

The most noticeable feature distinguishing the Lobster [2] ( Fig. 1 ) at first sight from other familiar animals is the jointed shelly armour that encases its body and limbs. Over the fore part of the body this armour is continuous, forming a shield, or carapace , which projects in front, between the eyes, as a toothed beak, or rostrum ; on the hinder part—the tail, or abdomen —it is divided into six segments, or somites , connected with each other by movable joints. Each of these somites carrie

Table of Classification of Crustacea Fig. 10—The "Fairy Shrimp" ( Chirocephalus diaphanus ), Male . × 2. (After Baird.) View larger image Occasionally there may be found in rain-water puddles and the like, in the South of England, a beautiful, transparent, shrimp-like animal, an inch or more in length, to which the name of "Fairy Shrimp" has been given ( Fig. 10 ). It is known in technical zoology as Chirocephalus diaphanus , and is a representative of the subclass Branchiopoda . The members of

The great majority of Crustacea are hatched from the egg in a form very different from that which they finally assume, and reach the adult state only after passing through a series of transformations quite as remarkable as those which a caterpillar undergoes in becoming a butterfly, or a tadpole in becoming a frog. Many of these young stages were known for a long time before their larval nature was suspected, and it is one of the curiosities of the history of zoology that, even after the actual

The tract of seashore which is laid bare by the retreat of the tide offers on most coasts a rich collecting-ground to the student of Crustacea. In places where shelving, weed-covered rocks run out to sea, innumerable Crustacea have their home in the rock-pools, or lurk in crannies awaiting the return of the tide. On sandy beaches, at first sight apparently barren of life, a closer search will reveal a whole fauna, amongst which burrowing Crustacea of various orders are prominent. Further, the sh

It has already been mentioned that the animals living on the sea-bottom in shallow water do not differ greatly in character from those that may be found between tide-marks. As we go farther out from land, however, into the deeper water, the character of the fauna gradually changes. One by one the species found near the shore become rare and disappear, and their places are taken by others characteristic of the intermediate depths. These in their turn give way to others, till in the abysses of the

It is only rarely that the floating organisms of the surface of the sea are so large or so abundant as to catch the attention of the casual observer. Except for an occasional shoal of porpoises or of flying-fish, the waste of waters seen from the deck of a ship in mid-ocean usually seems to be barren of life. Nevertheless, there is probably no region of the ocean where the tow-net will not reveal the existence of a more or less varied fauna and flora. Sometimes, indeed, these organisms, though m

The Crustacean fauna of fresh water is much less rich and varied than that of the sea. Although the number of individuals in a pond or lake may be enormous, they will be found to belong to a comparatively small number of species. All the subclasses of Crustacea with the exception of the Cirripedia have representatives in fresh water, but in most of them only a very few of the families and genera comprise truly fresh-water species. In spite of the comparative poverty of the fauna, however, it is

There is every reason to believe that the Arthropoda, like the other great groups of the animal kingdom, had their origin in the sea; but they must have invaded the dry land at a very early period, and most of the classes into which the group is divided—the Arachnids, Myriopods, and Insects—are now predominantly terrestrial in their habits. The Crustacea alone have remained for the most part aquatic animals, and only in a comparatively few cases have they succeeded in adapting themselves complet

The life of every animal is in more or less intimate relation with that of all the living creatures which surround it. Some serve for its food, or supply it with shelter or foothold; others prey upon it, or compete with it for the necessaries of life; and others, again, influence it for good or evil in countless ways more subtle than these, but equally important. There are some associations of a closer and more enduring nature, to which the names of Symbiosis, Commensalism, and Parasitism, are a

The Crustacea come into relation with human life in the most obvious and direct way in the case of those species that are used for food. The number of species so used in various parts of the world is very large, almost the only necessary condition being that the species shall be sufficiently large and abundant to make it worth while to fish for it. As most of the larger Crustacea belong to the Decapoda, it is this order that supplies practically all the edible species, almost the only exceptions

Since the acceptance by naturalists of the theory of Evolution as indicating the mode of origin of the various forms of life now existing, one of the chief lines of biological investigation has had for its object the reconstruction of the pedigree (or, as it is called, the "phylogeny") of the larger groups of the animal and vegetable kingdoms. In attempting to do this, there are three main sources from which evidence may be drawn. The results of Comparative Anatomy enable us to decide with more

It may be useful to give here a few hints as to the methods of collecting Crustacea. Of the species that live in the sea, many may be found between tide-marks by turning over stones and searching among sea-weeds and in rock crevices. A small hand-net, made by fastening a bag of coarse muslin to a stout wire ring of a few inches diameter, is useful for fishing in rock pools. Shore-collecting in this manner is most productive at spring-tides, when the deeper levels of the shore are open to explora