13G ELEMENTARY BIOLOGY. [Xll. 



7. The point of union of the appendages with 

 the somite. 



5. The sternum: that portion of the ventral sur- 

 face of the somite which lies between the 

 points of attachment of the app,endages. 



6. The epim^on : the portion of the ventral surface 

 which lies on each «ide 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. 



h. The appendages or swimmerets: one on each side : 



the structure of each — 

 I 



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



dite), consisting of a shorter proximal and a 



longer distal "piece. 



p. 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- 



