416 OHIO BIOLOGICAL SURVEY 



times the length of the body, the length of the posterior from 

 1/2-I times the length of the body; principal vacuole with small 

 accessory vacuole; rod-like organ slightly developed; movement 

 slow gliding, rarely a rotating free-swimming movement. 

 Habitat, fresh water. 



TABLE OF SPECIES. 



A^ Periplast without distinct spiral or long'itudinal striations. 

 Bi Cells normally straight. 



C Anterior and posterior ends blunt . . 1. H. acus 

 C- Anterior and posterior ends sharply pointed 2. H. acutissimum 

 B- Cells curved or twisted. 



Ci Curved or sickle like in form . . . 3. H. tremulum 

 C- Twisted into a form resembling spiral threads of 



a screw . . . . . . 4. H. spirale 



A- Periplast with distinct spiral or longitudinal striations. 

 B' Periplast longitudinally striate, length approximately 



250m. . . . • • • • 5. H. mutabile 



B= Periplast spirally striate, length 35-60/^. 



C Comparatively long, fusiform, twisted . 6. H. klebsii 



C- Compai-atively short, spherical or oval, not twisted. 



D' Secondary flagellum shorter than the body 7. H. nebulosum 

 D- Secondary flagellum longer than the body 8. H. globiferum 



1. H. acus (Ehrenb.) (Fig. 8, PI. XXIV). 



Fusiform with rounded ends ; periplast weakly striate spirally ; 

 primary flagellum slightly longer than body; secondary flagellum 

 about y-> length of body. 



L. 45-50/a. D. 8-20/x. 



Distribution, cosmopolitan ( ?) . Stagnant pools. 



2. H. acutissimum Lemm. (Fig. 9, PI. XXIV) . 



Elongately fusiform with pointed ends ; periplast smooth ; 

 primary flagellum as long as body; secondary flagellum 1 1/2-2 times 

 as long as body. 



L. 17/x. D. 2.5-3/x. 



Distribution, Europe. Pools with aquatic vegetation. 



3. H. tremulum Zach. (Fig. 10, PI. XXIV). 



Slightly lunate or curved, narrowed in front, broadly rounded 

 posteriorly ; periplast smooth ; primary flagellum somewhat longer 

 than body ; secondary flagellum 14 s,s long as body. 



L. 40/^. D.(?). 



