23 Branch Arthropoda. 



these, as the leech, the joints are very obscure. The bee, 

 then, which gives us food, is related to the dreaded tape- 

 worm, with its hundreds of joints, which, mayhaps, robs us 

 of the same food after we have eaten it; and to the terrible 

 pork-worm, or trichina, which may consume the very^ 

 muscles we have developed in caring for our pets of the 

 apiary. 



In classifying animals, the zoologist has regard not only 

 to the morphology— the gross anatomy— but also to the 

 embryology, or style of development before birth or 

 hatching. On both embryological and morphological 

 grounds, Huxley and other recent authors are more than, 

 warranted in separating the Vermes, or worms, from the 

 Articulates of Cuvier, as a separate branch. The remain-^ 

 ing classes are now included in the branch Arthropoda. 

 This term, which means jointed feet, is most appropriate,, 

 as all of the Insecta and Crustacae have jointed feet while 

 the worms are without such members. 



The body-rings of these animals form a skeleton, firm,, 

 as in the bee and lobster, or more or less soft, as in most 

 larvae. The hardness of the crust is due to the deposit 

 within it of a hard substance called chitine, and the firm- 

 ness of the insect's body varies simply with the amount of" 

 this chitine. This skeleton, unlike that of Vertebrates or 

 back -bone animals, to which man belongs, is outside, and thus- 

 serves to protect the inner, softer parts, as well as to give 

 them attachment, and to give strength and solidity to the- 

 animal. 



This ring structure, so beautifully marked in our golden- 

 banded Italians, usually makes it easy to separate, at sight,, 

 animals of this branch from the Vertebrates, with their 

 usually bony skeleton; from the less active Molluscan 

 branch, 'vvith their soft, sack-like bodies, familiar to us in. 

 the snail, the clam, the oyster, and the- wonderful cuttle- 

 fish — the devil-fish of Victor Hugo — with its long, clammy 

 arms, strange ink-bag, and often prodigious size; from the 

 branch Echinodermata, with its graceful star-fish and sea- 

 stars, and elegant sea-lillies; from the Coelenterata with its- 

 delicate but gaudy jelly-fish, and coral animals, the tiny 

 architects of islands and even continents; and from the- 



