ARTHROPOD A 267 



IV. Appendages. Group them into regions and notice 

 the general differences and the differences in the uses 

 to which they are put. If time will allow, study the 

 appendages in detail as follows; 



1. Begin with the third or fourth abdominal appendage (swimmerets) making 

 the drawings necessary to show the parts: 



Protopodite, or basal portion. 



Exopodite, or external branch. 



Endopodite or internal (median) branch. 



Compare all the abdominal segments with that studied. Do different indi- 

 viduals agree in the appearance of the first and second abdominal segments? 

 Compare the last segment (telson) with those studied. How many segments in 

 the abdomen? Of what parts is the tail fin made up? 



2. Cephalo-thoracic Appendages. Remove with scissors the over-arching 

 portion of the carapace and expose the base of the appendages. Find the third 

 maxilliped (the first appendage in front of 'the large claw). Remove by inserting a 

 scalpel and bringing away all that belongs to it. 



Identify : 



Protopodite, of two segments (coxopodite, next the body, and basipodite). 



Endopodite and exopodite. How many pieces in each? 



Epipodite, lying in the gill-chamber. Are there any special outgrowths on 

 it? 



Study and compare with this the large claw, and the other walking append- 

 ages. Which part is wanting in these, exopodite or endopodite? Reasons 

 for your view? How do these five appendages differ from each other. 



Examine and compare the appendages in front of the third maxilliped in 

 order: 



Second maxilliped. 

 First maxilliped. 

 Second maxilla. 

 First maxilla. 



Mandible. 



Antenna. 



Antennule. 



Head parts. 



What are the evidences that the antennae and antennules are homologous 

 with those already described ? 



Revise your estimate of the number of segments. 



Compare the appendages again by groups, and notice the chief points of 

 difference, and the ends served by these differences. Make a careful 

 sketch of each type of appendage, labeling all parts. (The names of the 

 segments of the larger appendages may be found in fuller texts, if desired.) 



By studying the living specimen, determine just the work done by each 

 of the types of appendages. 



Note the position of the eyes. Examine with a low power. 



In the basal joint of each antenna is the opening of the "green gland." 



In the basal joint of the antennules are the otocysts. (Statocysts.) 



