. Cassell's natural history. Animals; Animal behavior. LAND As we have already pointed out, tlie brancliiie or gills are enclosed between the side walls of the thorax and the over-spreading head-shield (the " Crab-cart" of peasants' children in tlie English Eastern Counties), and are borne upon the basal joints of the thoracic limbs. As rapidity of movement necessitates increased activity iii the circulation of the vital fluid in the body, we thus find that Tuy this simple arrangement the branchiie are brought directly into connection with the appendages specially engaged in
. Cassell's natural history. Animals; Animal behavior. LAND As we have already pointed out, tlie brancliiie or gills are enclosed between the side walls of the thorax and the over-spreading head-shield (the " Crab-cart" of peasants' children in tlie English Eastern Counties), and are borne upon the basal joints of the thoracic limbs. As rapidity of movement necessitates increased activity iii the circulation of the vital fluid in the body, we thus find that Tuy this simple arrangement the branchiie are brought directly into connection with the appendages specially engaged in locomotion. In a precisely similar manner we observe that the pectoral muscles in the bird, by their rapid action, accelerate their respiratory functions, consequently those birds whose flight is swiftest, such as the Swallows, naturally breathe most .quickly. Amongst the Land and Shore Crabs, such as the Grapsidcv, tlie Ocypodidw, the Gecarcinidce, we find some of the most rapidly moving terrestrial forms of Crustacea. Respiration in these Crabs is, however, carried on essentially upon the same plan as in th'=' aijuatic species, that is, by of moistened branc/na or gills, not by pulmonary sacs, as in the Ai-achnida, nor by trachea, as in insects proper. Nevertheless, the aeration of the blood in the branchias of Land Crabs is so much more comjjlete than it is among the aquatic species, that the Land Crabs are easily drowned by continued immersion in water. Land Crabs are met with in the tropics in vast numbers. Of these, the most common and best know n to us is the Gecarcinus ruricola, or " Countryman Crab,' once so abundant in the highlands of Jamaica, and still so formidable in Montserrat and other West Indian sugar-producing Islands (Fig. 17). When the season foi -sjjawning arrives vast armies of them set out from the hills, and, undaunted by opposition, march in a direct line towards the sea-shore for the purpose of depositing their eggs. Having reached the de
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