IXVERTEBHATES. ROIWDWORMS 41 



in each alcove are anatomical, i. e. so constructed as to show the internal 



organs of typical meniliers 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 animalcules comprise many exquisite and 



grotesque forms, some of which construct tubes of gela- 



„ .J^ tinous substance, sand-grains, etc. A few of the species 



Rotifers . ,- , ,• ,. • , 



are parasites, l3ut most of them live a free, active live. 



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 



r. ■., . J are marine, although a few occur in fresh water. 



Sea-Mats and 



Lamp-Shells '^^^ lamp-shells shown in this alcove superficially 



resemble clams, but by structure are more closelj- related 



to the worms and starfishes. 



Alcove 8 is occupied by the sea stars, sea urchins, sea-cucumbers 



and sea lilies. The sea-star is the pest of the oyster beds, 



cove where it feeds on oysters and destroys them in large 



Sea-Stars and . "^ ' ^ 



Their Relatives numbers. The brittle stars are so called because oi their 



habit of dropping off one or more arms when handled or 



attacked. These, however, are later regenerated. 



The annulates, typified by the familiar earthworm, are worms 



whose bodies are made up of rings or segments They 



, ^ are inhabitants of both fresh and salt water, many 



Annulates ,.,,.. . , ,. , , ■, 



kinds living m 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 



. . , this group is greater than that of all the rest of 



Arthropods o i o 



the animal and vegetable kingdoms together. No other 

 group comprises so many species useful or harmful to man. In the case 

 in the center of the alcove is a model showing the anatomy of the 



