MEDUSA BIFIDA. 133 



Plate XX. Fig. 23. Medusa with four lobes or arms. 



24. Monstrous Medusa. 



25. Medusa 50 days old, not having undergone any metamor- 



phosis. 

 Natural size, figs. 1, 6 : 10-14 : 1&-22. 



Plate XXI. 



Fig. 1. Vorticella, enlarged. 



2. Extremity of a branch of the same, magnified. 



3. Vorticella of another species, enlarged. 



4. Vorticella stmtoria ; group. 

 0. Part of the group magnified. 



