THE LIVING WORLD 191 



tunicates, sea-squirts, or ascidians (Fig. 27). There is, 

 further, an immense group of arthropods, consisting of 

 all insects, crab-like creatures, hundred-legs and their 

 allies, with spiders, scorpions, tics and mites. We 



FIG. 26. 



HORSE-TAIL (Equisetum drummondii). 



have also the sub- kingdom of shell-fish or molluscs, 

 including cuttle-fishes, snails, whelks, limpets, the 

 oyster, and a multitude of allied forms. A multi- 

 tudinous sub-kingdom of worms also exists, as well as 



