190 DESCRIPTION OF [Poly gastric a. 



matter can be discharged from an opening in the end of 

 each lorica. Found with slimy and decaying portions of 

 water plants, &c. Size l-2180th to 1-1 150th. Length of 

 chain l-570th. 



182. ABTHRODESMUS pectinatus. 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. The 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 l-570th. 

 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 l-570th. 



185. ARTHRODESMUS octocornis. The eight-horned 

 Arthrodesmus is green, slightly compressed, and quadran- 

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

 Size l-1150th 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, 1 -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-like bodies is composed of a single pair 



