148 THE BIOLOGY OF THE ANIMAL 



rior, the second maxilla. "What segments are 

 lacking on this appendage? What pecuhar modi- 

 fication of the coxopodite and basipodite do you 

 find? Did you find anything similar on the other 

 appendages? Note the large plate-like expansion 

 or scaphognathite. To what is it fastened ? To 

 what does it correspond on other appendages? 

 What is its position in the gill-chamber? Draw. 

 Eemove the next appendage, the first maxilla, and 

 compare with the preceding. Draw. 



The next appendage towards the front is the man- 

 dible or jaw. Eemove this and examine the structure 

 of the protopodite. What is the position of the teeth ? 

 How many are there ? Is the number the same on the 

 other mandible ? Note the palpus, which here repre- 

 sents the endopodite. What segments are lacking? No- 

 tice lying just back of the mandible a thin, plate-like ex- 

 pansion, the metastoma, and in front, another shield- 

 shaped piece, the labrum. What is their relation to 

 the mouth opening? What is their structure? Are 

 they appendages ? Why ? Draw the mandible, meta- 

 stoma, and labrum. 



Note the opening of the mouth, its shape and size. 

 Notice also that it opens directly upward. 



Eemove the next two appendages, the antenna and 

 the antennule. Examine the first. What segments can 

 you find ? Note the long feeler. Which segment does 

 it represent? How many joints has it? Is it hollow 

 or solid? What is its range of motion? Note the 

 tubercle on the lower side of the coxopodite. What is 

 its color ? Note the opening. Draw. Are these open- 

 ings in the antenna, the openings of ducts of the 

 " green gland" homologous with those on the thoracic 

 appendages ? Why ? 



