HOMARUS AMERICANUS MILNE-EDWARDS 141 



jointed protopodite, five-jointed endopodite, exopodite, with flagel- 

 lum, epipodite and gill or podobranchia. Label coxopodite, baso- 

 podite, ischiopodite with comb, meropodite, carpopodite, propodite, 

 and dactylopodite. 



1 6. Make a drawing of the first pereiopod with the toothed 

 claw showing also epipodite and podobranchia. Label all joints 

 and be careful to represent correctly the interlocking mechanism 

 between the coxo- and ischiopodite and the breaking plane be- 

 tween the baso- and ischiopodite. Indicate by dotted lines the 

 axis of every articulation for comparison with third and fifth 

 pereiopods. 



17. Make a drawing of the third pereiopod showing all struc- 

 tures including epipodite, podobranchia and, if the specimen is 

 a female, opening of the oviduct. Label all joints and indicate 

 by dotted lines the axis of all articulations. 



18. Do the same with the fifth pereiopod, which has an epipo- 

 dite, but no podobranchia. If the specimen is a male, show the 

 opening of the vas deferens. 



19. Injected specimen. Cut away the left branchiostegite by 

 an incision along the branchiocardiac and left cervical line, ex- 

 posing the left branchial cavity. Make a natural-size drawing 

 showing the gills in situ. Of the outer gills the anterior six are 

 podobranchia, the hindmost the pleurobranchia of the fourteenth 

 segment. The lamellae between the gills are the epipodites. 

 Protruding from under the ends of the podobranchiae the ends 

 of the arthrobranchiae and pleurobranchiae are visible. 



20. Remove the podobranchiae and epipodites by cutting them 

 at their base, being careful, however, not to disturb the other 

 gills. This exposes all arthrobranchiae. Make a drawing of 

 them in situ and label anterior and posterior arthrobranchiae of 

 every somite. 



21. Remove all arthrobranchiae. This will expose the four 

 pleurobranchiae, while the attachment places of the removed 

 gills will appear as round holes. Make a drawing and label 

 somites. 



