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, withits 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 Crustace 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 
larva. 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, with 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 Celenterata with its 
delicate but gaudy jelly-fish, and coral animals, the tiny 
architects of islands and even continents; and from the 
