190 DESCRIPTION OF [Polygastrica. 



matter can be discharged from an opening in the end of 

 each lorica. Found with sKmy and decaying portions of 

 water plants, &c. Size 1-2 180th to 1-1 150th. Length of 

 chain l-570th. 



182. ARTHRODESMusj9ec^ma^M5. The comb Arthrodesmus 

 is green, fusiform, or oblong in shape ; from four to eight 

 are associated together, the exterior ones being seminulate. 

 Size 1-1 150th to l-860th. Found with Micrasterias. 



183. Arthrodesmus acutus. Tlie changing Arthrodesmus 

 is green and spindle-shaped, or oblong in form. In self- 

 division, each adjoining one slips below the level of its 

 neighbour, while the alternate ones remain. Size 1-5 70th. 

 Found with oscillatoria, especially in the month of July. 



184. Arthrodesmus convergens. The embracing Ar- 

 throdesmus is connected in pairs, as in fig. 112, or in four, 

 as in fig. 113. In the latter, the two middle ones are 

 produced from gemmae. Colour green. Size 1-5 70th. 



185. Arthrodesmus octocornis. The eight-horned 

 Arthrodesmus is green, slightly compressed, and quadran- 

 gular, each having four horns. Found with Navicula, &c. 

 Size 1-11 50th to l-1200th. 



186. Arthrodesmus truncatus is green, slightly 

 compressed, companulate, and truncated. They occur in 

 pairs, having the sides spinous. Found with Euglena 

 sanguinea. Size, including spines, l-480th. 



Genus LI. Odontella. The tooth-chained Animal- 

 cules comprised in this small genus are unattached and 

 free, having a simple univalved compressed lorica, and 

 multiply by an incomplete spontaneous self-division, in 

 the form of flat articulated ribbons or chains ; each link 

 of such chain-Hke bodies is composed of a single pair 



