DAPHNIA : A STCDY OF THE FOOD OF FJSUEH 159 



f. 



>r^"' 



^j^ 



Fig. 156. — Acartia, a marine Copepod. Greatly magnified. Photo, by 



W. H. C. P. 



seashore between tide-marks (Fig. 157). If j-'ou watch barna- 

 cles in rock pools, you can see them open the valves of their 



Fig. 157. — Mussel-shell bearing barnacle,s (Balanus). Photo, by W. H. C. P. 



