38 



THE MICROSCOPE AND ITS REVELATIONS. 



a deep equatorial furrow, , whilst the flagellum-bearing hemisphere, A, 

 has a deep meridional groove on one side, J, extending from the equatorial 

 groove to the pole; the flagellum taking its origin from, the bottom of this 

 vertical groove, near its junction with the equatorial. The cilia, in this 

 form, do not seem to be disposed in special bands, but are distributed 



FIG. 300. 



Peridinium uberrimum; A, B, Front and back views; c, Encysted stage ; D, Duplicative subdivi- 

 sion. 



over the general surface of the body; but in several other Peridinians 

 (Fig. 301), whose bodies are partially invested by a firm lorica, the cilia 

 are arranged in special zones. It is questionable whether any definite 

 mouth exists in this type; but it seems certain that alimentary particles 



FIG. 301. 



1, Ceratium tripos; 2, Ceratiumfurca. 



are received into the interior of the body, becoming inclosed in c diges- 

 tive vesicles.' A ' contractile vesicle' has been rarely observed; but a 

 large nucleus, sometimes oval, and sometimes horseshoe-shaped, seems 

 always present. The Peridinia multiply by transverse fission (Fig. 300, 

 p), which commences in the subdivision of the nucleus, and then shows 

 itself externally in a constriction of the ungrooved hemisphe re, par 



