32 VARIATION. STRUGGLE FOR EXISTENCE 



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

 Alcove 8 an< ' sea-lihes. The sea-star is the pest of the oyster beds, 



Sea-Stars where it feeds on oysters and destroys them in large 



and Their numbers. The brittle stars are so called because of their 

 Relatives 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 worms 

 whose bodies are made up of rings or segments. They are inhabitants 

 Alcove 9 of both fresh and salt water, many kinds living in the mud 



Annulates 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 unin- 

 habited 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 

 Alcove 10 than that of all the rest of the animal and vegetable king- 



Arthropods doms 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 common lobster, also enlarged models 

 showing heads of various species of insects. On the wall are the two 

 Crustaceans largest specimens of lobster that have ever been taken. 

 and Insects They weighed when alive thirty-one and thirty-four pounds 

 respectively. The largest of the arthropods is the giant crab of Japan, 

 which, like that placed on the wall, may have a spread of about ten 

 feet. The main exhibit of insects is displayed on the third floor. 



The Mollusks form a group second only to the arthropods in the 



vast number and diversity of forms which it embraces, including marine, 



fresh-water and land animals. All mollusks have soft 

 Alcove X] 

 Mollusks bodies, but nearly all of them secrete a shell which in many 



species is of pearly material (mother-of-pearl) . Well-known 



Models of examples of this group are the common clam and oyster, 



Clam and an( j en ] ar g ec i models in the center case show the anatomy 



ys e of this species. A large collection of mollusks is shown 



on the third floor. 



Vertebrates include the largest, most powerful and most intelli- 

 gent of animals. This group culminates in man, who still bears witness 

 to his chordate ancestry in the retention of a chorda (cartilaginous 

 spine), and gill clefts during embryonic life. Among these ances- 



