CHAPTER IV 



ADAPTATION TO SURROUNDINGS 



A Study of Crustacea 



To Show the General Adaptation of an Invertebrate to its 

 Surroundings 



I. A STUDY OF CRAYFISHES 



Materials. 



Crayfishes, living and preserved. Some of the living 

 crayfishes should be established in conditions as natural 

 as possible i.e. in an inch or so of fresh water, with rocks, 

 weeds, etc., and left undisturbed. Small crayfishes are 

 desirable to show locomotion in, water. 



Living Crayfishes 

 Directions and observations. 



I.. Observe living crayfishes in their usual habitat or 

 in a large aquarium, without disturbing them, and see 

 where they stay when they are free to choose. Notice 

 their position. What senses are on guard .' What is 

 the color of the head and claws ? How may this color 

 aid the animal in getting food or in escaping enemies ? 

 Why is the color of the posterior region less important 

 than the color of the anterior 1 



2. Offer them bits of meat. If one takes food, notice 

 the appendages it uses. How does it discover the food .' 



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