SQUILLA. 149 



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. 



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

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



(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 chelae? 



(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 

 the oviducts is in the mid-ventral line, on the antepenultimate 

 thoracic segment. Examine the chelae and compare them with 

 the chelae of a lobster. Are they homologous appendages in the 

 two animals? If you have living specimens, study their move- 

 ments while walking and swimming. 



A drawing of a side or ventral view will be profitable. 



Internal Anatomy. 1. Remove the top of the carapace and 

 abdomen. Beneath the muscles note the elongated, white tube, 



