The Lobster. 81 



and sixth. The appendages of the first abdominal segment 

 are different in the two sexes. Do you find any trace of 

 appendages on the terminal segment or telson? 



Examine one of the thoracic appendages and endeavor to 

 homologize the parts with the parts of the pleopoda. Pass 

 to the third maxilliped and see if it has a protopodite, an 

 exopodite, and an endopodite. Return now to the ambula- 

 tory appendage and see if you are better able to homologize 

 its parts, so far as they are present, with parts of the abdomi- 

 nal appendage. (The ambulatory appendage is really an 

 endopodite supported on a strengthened protopodite.) 



Carefully remove the second ambulatory appendage of the 

 left side and draw it as seen from the front, naming the 

 parts. The proximal part of the protopodite bears a finely 

 lamellate gill and a posteriorly directed membranous out- 

 growth, the flabellum. 



Remove the remaining ambulatory appendages of the 

 same side and see if all agree in structure. (Other gills sit- 

 uated higher up, on the epimera, will be considered later.) 



Has the third maxilliped a gill ? A flabellum ? Remove, 

 and draw as seen anteriorly, naming the parts. 



After carefully removing the second maxilliped and noting 

 the rudimentary condition of the gill, the reduced flabellum, 

 and the number of divisions of the entopodite, draw as 

 above directed. 



The first maxilliped is without a gill, though its flabellum 

 is remarkably developed. The flattened, elongated exopo- 

 dite and endopodite extend anteriorly from the lateral 

 angle, while the internal part of the protopodite is greatly 

 enlarged and lobe-like. 



Draw. 



The second maxilla is even further altered : no gill is 



