30 CRUSTACEA 



(6) Means of defense — which do thej^ do first, flee or 



fight? 



(7) In flight, what kind of locomotion do they use? Just 



how is it performed? 



(a) Give two reasons why they go backward. 



(b) Molest one from behind. What does it do? Wh}^? 



(8) Try experiments to discover their range of sight. 



(a) What part of a circle can a crayfish see, since it can- 



not turn its head? How? 



(b) Can it see if there are any obstacles in its way when 



it darts backward? 



(9) Find out if the surface of the body is sensitive to the 



touch. 



(10) See if you can find any reason for two pairs of antennae. 



(11) Find out if the crayfish can hear, smell, or taste. 



(12) Determine the direction of the gill-currents by placing 



a drop of ink near the anterior edge and one at the 



posterior edge of the carapace. 

 3. Development. 



In early spring females with large, berry-like clusters of eggs, 

 under the abdomen, will be found. 



(1) To what are the eggs fastened? How? 



(2) Take these female specimens to your aquarium and 



watch the eggs till they are hatched. 



(3) The young. 



(a) Do they differ from the adults? If so, how? 



(b) Are they freed or attached to the mother? If at- 



tached, how? 



(c) Do they feed themselves, or are they fed by the 



mother at first? 



(d) What is their food? 



(4) Molting. 



(a) Watch carefully for the process of molting. 



(b) How does the crayfish get out of its shell? 



(c) Did any accident happen to it while it w^as getting 



out? If so, what? 



(d) In what condition is the body when the shell is first 

 removed? 



(e) W^here does the newly molted crayfish stay? 



