which gives the name to the species. Klebs maintains that the two
furrows are not connected, but in this he is certainly mistaken,
provided we have the same species under consideration. Very common
about Woods Hole.

Length from 40 to 50µ; width 30µ; thickness 15µ.


[Illustration: Fig. 27.--_Amphidinium operculatum_.]



KEY TO INFUSORIA.

1. With cilia Subclass _Ciliata_. 3

2. Without cilia (in adult state) Subclass _Suctoria_
tentacles

3. a. Without a specialized fringe of Order _Holotrichida_
large cilia (ad. zone)

b. With general covering of cilia Order _Heterotrichida_
+ adoral zone

c. With cilia on ventral side Order _Hypotrichida_
+ adoral zone

d. With cilia in region of adoral Order _Peritrichida_
zone, and about mouth only