OtJier hivcrtcbrate-Animal Study 471 



Describe the antennules of each side and tell how they differ. Can you 

 see the little fingerlike organs which clasp above the antennae and below 

 the antennules on each side of the head ? Can these be moved ? 



9. Look at the crayfish from above. How many segments are there 

 in the abdomen? Note how graceful the shape of each segment. Note 

 that each has a fan-shaped piece down the side. Describe how theedges 

 of the segments along the sides are margined. 



10. Of how many pieces is the tail made? Make a sketch of it. 

 How are the pieces bordered? Can the pieces shut and spread out side- 

 wise? Is the tail hinged so it can be lifted up against the back or curled 

 under the body? 



1 1 . Look underneath the abdomen and describe the little fringed 

 organs called the swimmerets. How many are there? 



12. How does the crayfish swim? \Vith what does it make the 

 stroke ? Describe carefully this action of the tail. "When it is swimming, 

 does it use its swimmerets? Why do not the many legs and big nippers 

 obstruct the progress of the crayfish, when it is swimming? 



13. When does the crayfish use its swimmerets? Do they work so as 

 to push the body backward or forward? Do you know to what use the 

 mother crayfish puts her swimmerets? 



14. Do you know how crayfishes breathe? Do you know what they 

 eat and where they find it? 



15. Where do you find crayfishes? Where do they like to hide? Do 

 they go headfirst into their hiding place, or do they back in? Do they 

 stand ready to defend their retreat? When you look down into the 

 brook, are the crayfishes usually seen until they move? Why is this? 

 Where do the crayfishes pass the winter? Did you ever see the crayfish 

 burrows or mud chimnies ? 



16. If the crayfish loses one of its legs or antennae, does it grow out 

 again? How does the crayfish grow? 



17. Put a crayfish in an aquarium which has three inches of coarse 

 gravel on the bottom, and watch it make its den. How does it loosen up 

 a stone? With how many legs does it carry its burden of pebbles when 

 digging its cave? How does it use its jaw-feet, its nippers, and its first 

 and second pairs of walking legs in this work? 



'.4 rock-lined, wood-embosomed nook, 

 Dim cloister of the chanting brook/ 

 A chamber within the channelled hills. 

 Where the cold crystal brims and spills. 

 By dark-browed caverns blackly flows, 

 Falls from the cleft like crumbling snows, 

 And purls and splashes, breathing round 

 A soft, suffusing mist of sound.'' 



— J. T. Trowbridge. 



