Branch Arthropoda 63 



end. The remaining tapering segments make up the 

 abdomen. Observe the broad dome-shaped carapace 

 making up the anterior part of the cephalothorax. 

 Compare this with the carapace of the lobster in posi- 

 tion and shape. If the specimen is a female, a pair of 

 egg sacs may be seen attached to the iirst abdominal 

 segment. Study the greatly developed posterior seg- 

 ment of the abdomen, with its branched projections. 

 Observe the yellow outline of the intestine showing 

 through the wall of the abdomen. Dark masses show- 

 ing through the carapace are the reproductive organs. 

 Near the anterior edge of the carapace on the median 

 line, find the dark purple eye-spot : this is really made 

 up of two disks which may be seen with the high 

 power. 

 II. — Lateral or Ventral View. Obtain a good lateral or 

 ventral view, if necessary using the needles in manipu- 

 lation. The most noticeable appendages of the cephalo- 

 thorax are the long-jointed antennae. Just back of 

 these another smaller pair, the antennules, may be 

 found. Just below the two pairs of antennae the 

 mouth parts surrounding the mouth are grouped, 

 although it may be quite difficult to distinguish clearly 

 the pair of mandibles and the two pairs of maxillae. 

 At some distance behind the mouth parts are the four 

 pairs of thoracic appendages, the legs. Study the 

 segmentation of the legs, and try to make out a fifth, 

 rudimentary pair. 



