170 THE BIOLOGY OF THE ANIMAL 



dish containing a live lobster or crayfish ■which 

 has had nothing to eat for three or four days, 

 and, at some distance from the animal, with a 

 pipette quietly force a current of water from 

 the meat towards the animal. Does the latter 

 show by its actions that it is conscious of the 

 presence of the meat? How does the animal 

 behave ? Do you notice any peculiar motions 

 of the antennae or antennules ? How long be- 

 fore it recognizes the presence of the meat ? 

 Can you decide definitely whether its actions 

 are due to the sense of smell or that of taste ? 

 4. Sight. — Find a specimen which is lying quietly 

 near the side of the aquarium. Move your 

 hand quiclvly past the animal. Is it at all 

 disturbed? Watch several which are moving 

 around. Do any of them show that they can 

 see the others coming from a distance ? Do 

 the eye-stalks move in such a manner as to per- 

 mit the animal to look in different directions ? 



General Questions. — Considering the appendages mor- 

 phologically, in what various ways do you find segments 

 of the typical appendages modified ? Examine again 

 all of the appendages, and write a list of the modificar 

 tions of structure found on each. From this list make 

 another, giving all of the variations found. Is any one 

 segment more susceptible to variation than the others? 

 If so, can you give any reasons for it ? 



Eeview all of the appendages from a physiological 

 rather than a morphological point of view. Examine 

 each appendage by itself, and write out a list of all the 

 functions which you know each appendage to be capable 

 of performing. Then from this list make a second, 



