PLATE XIX. 







Fig. 1. — Phyto-plankton, consisting of 

 the Diatom Rhizosolenia semispina. 



Fig. 2. — The Diatom Chcetoceras deci- 

 piens. 



Fig. 3. — Zoo-plankton, consisting of 

 the Copepod Calanus finmarchicus. 



All magnified. 



Fig. 4. — The Copepod Acartia clausi. 



[Photo-micrographs by A. Scott. 



