146 ARTHROPODA. 



(d) The mouth parts consist of mandibles and two maxillce. 



4. If the specimen is a female it may have two large egg sacs 

 attached to the sides of the base of the abdomen. The female 

 has two of the abdominal segments fused. In the male the seg- 

 ments are free. 



A drawing of the specimen is desirable. 



ARGULUS. (Fish-Louse.) 



These animals may be found on many species of fresh-water 

 and marine fish. Notice their shape and determine how they 

 cling to their host. Are they able to crawl? Can they swim? 



1. Into what regions can the body be divided? 



2. Examine the appendages and find: 



(a) The eyes, the eye-spot, and the two pairs of small 

 antennae. 



(b) The sucking proboscis, composed of mandibles and max- 

 illce, which lies between the suckers. 



(c) The suckers, which are the modified second maxillce. 



(d) The posterior (third) maxillipeds just behind the suckers. 



(e) Four pairs of biramous thoracic appendages. What is 

 their function? 



Make a drawing of the animal. 



LEPAS. (Goose-Barnacle.) 



If possible, examine a cluster of specimens as they naturally 

 occur attached to floating timber. 



1. Why are the peduncles much larger in some specimens 

 than in others? Are they contractile so the body may be moved 

 into different positions? Would such movements be of value? 



2. Notice the abdominal appendages. Can they be thrust 

 from the shell? What is their character? What are their char- 

 acteristic movements? Drop a small piece of clam meat on 

 these appendages of a living specimen and see what happens. 

 What kind of food would they naturally collect? 



3. Examine the portions of the shell. The portion on the 

 closed, dorsal margin is the carina, laterally and near the base 



