136 ELEMENTARY BIOLOGY. [XII. 



7. The point of union of the appendages with 

 the somite. 



. The sternum: that portion of the ventral sur- 

 face of the somite which lies between the 

 points of attachment of the appendages. 



. The epimeron : the portion of the ventral surface 

 which lies on each side external to the attach- 

 ment of the appendage. 



This region is very short and passes almost 

 directly into the inner walls of the pleuron. 



f. The downward extension (pleuron) of the 

 lateral walls of the somite formed by the pro- 

 longation of the tergum and epimeron: the 

 smooth facet on the anterior half of the 

 pleuron where it is overlapped by the one in 

 front. 



b. The appendages or swimmer ets: one on each side : 

 the structure of each 



a. The short two-jointed basal portion (protopo- 

 dite), consisting of a shorter proximal and a 

 longer distal piece. 



yS. The antero-posteriorly flattened elongated la- 

 mellae attached to the distal joint of the 

 protopodite, an inner (endopodite) and outer 

 (exopodite). . 



3. The fourth and fifth abdominal segments: closely 

 resembling the third. 



4. The sixth abdominal segment : its modified append- 

 ages. 



