HIPPA. SQUILLA. 139 



shells and watch the crabs test them to see which will serve 

 best. 



A drawing is desirable. 



HIPPA. (Sand Mole.) 



On sand beaches, between low- and high-water mark, there 

 may frequently be seen the shallow depressions that mark the 

 places where these animals have burrowed. They may be dug 

 out with a shovel, but they quickly disappear again. 



1. Notice their shape and the ease and rapidity with which 

 they burrow. 



2. Place specimens in a dish containing sand and a little sea- 

 water and try to determine just how the burrowing is done. This 

 may frequently be done by holding a specimen so it just touches 

 the sand. Which end goes into the sand first? Notice the posi- 

 tions in which the appendages are held. Does this have any- 

 thing to do with the direction in which it burrows? Does the 

 animal jump or crawl ? In what direction and how can it swim ? 



3. Examine the body and see if it is divided into head, thorax, 

 and abdomen. Why has the telson such a peculiar shape ? 



4. Examine the appendages. 



(a) The stalked eyes. 



(b) The biramous antennules and the exceedingly long, feath- 

 ery antennce. What is the usual position of the antennse ? 



(c) The mouth appendages. Are strong, hard mandibles 

 present ? What must the character of the food be ? 



(d) The thoracic appendages. How many are there? Are 

 they similar? Are there any chelse? 



(e) The abdominal appendages. Are they all alike? What 

 functions are performed by them? 



Make a drawing. 



SQUILLA. 



Compare the animal carefully with the lobster, noting all of 

 the important differences. The posterior three thoracic seg- 

 ments are free. The male possesses a copulatory organ on the 

 basal joint of the last thoracic leg. In the female the opening of 



