

INVERTEBRATES. ANTHROPODS 29 
[Note for teachers and students—Some of the models in each 
alcove are anatomical, i. e., so constructed as to show the internal 
organs of typical members of each group. In such cases, arbitrary 
colors chosen to designate the various systems of organs are adhered 
to consistently throughout the series. For example, the digestive 
system is shown in yellow, heart and blood-vessels in red, organs of 
excretion (kidneys) in green, reproductive system in gray, and the brain 
and other parts of the nervous system in black or neutral color.} 
The minute wheel animacules comprise many exquisite and 
grotesque forms, some of which construct tubes of gela- 
ae tinous substance, sand-grains, etc. A few of the species 
are parasites, but most of them live a free, active life. 
‘They are aquatic and found mainly in fresh water. 
The sea-mats in Alcove 7 are plant-like animals which lead the 
colonial form of life. The majority of the species 
Alcove 7 are marine, although a few occur in fresh water. 
Sea-Mats and : : , 
Lamp-Shells The lamp-shells shown in this alcove superficially 
resemble clams, but by structure are more closely related 
to the worms and starfishes. 
Aleove 8 is occupied by the sea stars, sea urchins, sea-cucumbers 
and sea lilies. The sea-star is the pest of the oyster beds, 
Pago ae where it feeds on oysters and destroys them in large 
Their Relatives numbers. The brittle stars are so-called because of their 
habit of dropping. off one or more arms when handled or 
attacked. These, however, are later renewed. 
The annulates, typified by the familiar earthworm, are worm 
whose bodies are made up of rings or segments. They 
Alcove 9 , : 
aoe are inhabitants of both fresh and salt water, many 
kinds living in the mud and sand of the shore while 
others bore into wood and shells. The marine annulates are often 
very beautiful in color and greatly diversified in form and habits, as 
illustrated by the models, many of which are greatly enlarged. 
The “houses” that these annulates build are often very beautiful 
and interesting. In the window is a group showing a section of mud 
flat on the New England coast, with the variety of worm-life found 
in what to the casual observer seems to be an uninhabited area, and 
illustrating some of their habits. 
Arthropods include the familiar crabs, lobsters, insects and 
their relatives. The number of existing species in 
crete this group is greater than that of all the rest of 
the animal and vegetable kingdoms together. No other 
group comprises so many species useful or harmful to man. In the case 

