PALINURUS OR THE SPINY LOBSTER OF BOMB A Y. 367 



Were it not for this buttoning arrangement the posterior portion 

 of the carapace might be tilted upwards and the gills exposed, as the 

 articulating membrane between it and the first abdominal tergum is 

 loose to allow of free flexion and extension. 



We have seen that the abdominal appendages are paddle-shaped in 

 accord with their function as swimming organs. The cephalo-thoracic 

 appendages are formed on the same plan but with considerable 

 modification in structure to adapt them for different functions. 



Without counting the eye-stalks, they are from before back- 

 wards. 



of I. A pair of antennules 1 Main function organs of sense 

 <8 "§ II. A pair of antenna? J or " feelers ". 



r% -= <{ III. A pair of stout mandibles "1 



eL'B I IV. A pair of first maxilla? )» Jaws. 



^ { V. A pair of second maxilla? J 



f VI. A pair of first maxillipeds ") 



VII. A pair of second maxillipeds ^Foot-jaws. 



VIII. A pair of third maxillipeds J 



IX. A pair of first walking legs 



-4-3 



cs __§ ] X. A pair of second do. 



§ XI. A pair of third do 



a. 



< 



XII. A pair of fourth do. 



^XIII. A pair of fifth do. 



In Plate B the appendages are indicated by these numerals. 



Remove the gill-cover of one side with stout scissors, cutting from 

 behind forwards a little external to the branchio-cardiac groove. 

 Keep the scissors close to the gill-cover or you may cut the gills. 

 Make a second vertical cut at right angles to the first, a little behind 

 the cervical groove. Count the gills and note the position in which 

 they are attached. You will find on moving the last walking leg to 

 and fro that none of the gills are disturbed, but on moving any of 

 the other walking legs or the second or third maxilliped, a gill and 

 also a membranous flap is moved to and fro with the limb. These 

 gills as they are attached to the legs are known as foot-gills or podo- 

 branchice (Greek pons, podos, a foot ; branchia, a gill). 



Of the other gills you will find four are attached to the epimeron 

 or the inner wall of the chamber. As they are opposite the last 



