INVERTEBRATE ZOOLOGY. 93 



6. The second and first ma.vUlipeds. Remove these in oi'der and com- 



pare with the third. Which terminal branch shows a gradual reduc- 

 tion ? Which one shows increase ? Can yon homologize the parts of 

 the endopodite in eachV Look for a gill and an epodite in each. 

 Notice in the first, the flattened maxillary processes, projecting in- 

 wards. There are two of these, corresponding to the two divisions 

 of the protopodite. 



7. The second maxilla. Do yoti recognize in this an exopodite? An 



endopodite V An epipodite V With what is the epipodite f nsed ? 

 How many maxillary processes are there ? Can you explain them 

 with reference to those of the preceding ? 



8. The first maxilla. Which of the two terminal branches fails here 'i 



Can you homologize the maxillary processes ? 



9. The mandible. This consists of a hard jaw with toothed edges and a 



palpus. What typical part does each represent? Compare with 

 last. 



10. The second antennae. These consist of a in-otopodite and the two 

 terminal branches. Which one is developed into the long, tactile 

 portion V Notice at the base, the conspicuous opening of the nephrid- 

 ial organ, the so-called "green gland," situated in the center of a 

 raised papilla. 



11. The first antennae {antenmdae). These are biramous. Upon one 

 of the branches are situated tufts of club-shaped hairs, probably 

 olfactory. Examine both branches with the microscope and find out 

 which one possesses them. Examine the base of these antennae for 

 the auditory organs, little cavities open to the air, into which the 

 animal pushes sand-grains to serve as otoliths. 



12. The eyes. These have been supposed to have the value of append- 

 ages, being movably articulated with the body, but they develop as 

 fixed parts and become secondarily free. 



The number and relationships of appendages and somites in Crustacea may 

 be expressed bj' formulae. An X denotes that a part is present ; R signifies 

 that a part is rudimentary ; — that it fails. Simple abbreviations may be 

 used for the names of the appendages, Roman numerals for the somites of the 



