Sketch of the Infusoria of the family Badllaria. 297 



The reader is requested to compare some of the figures last 

 referred to with the descriptions of Desmidium hexaceros and D. 

 aculeatum, page 289. 



14. Euasirum . (Fig. 14, PI. 1.) Binary, corpuscles trian- 

 gular, each angle terminating in a sharp spine. Hab. West Point. 



I have seen several other species of Euastrum, but the number 

 figured is sufficient to give an idea of the variety and beauty of 

 the forms in this interesting genus. 



Clostebium. (See Figs. 30 to 38, PI. 1.) 



Ehrenberg makes of this genus a distinct family of Infusoria, 

 which he calls the Closterina, and characterizes thus : 



^'Poll/gastric [distinctly or probably) icithout alimentary ca- 

 nal, without appendices, polypidoms having the form of a wand, 

 (" baguette,''^) thread or spindle, by spontaneous division, papillcB 

 fixed and movable in the opening of the carapaceP 



I have before stated that I consider the genus Closterium most 

 closely related to Euastrum, and therefore with the Desmidiacea 

 generally. This relation to Euastrum is manifest in their apparent 

 identity in internal structure, the chief difference between them 

 is only in the external forms, and even in them, we find there is 

 a perfect transition from the highly lobed and tabular forms of 

 some species of Euastrum, to the entire, elongated and fusiform 

 species of Closterium. It is therefore without hesitation that I 

 place Closterium (as indeed most writers do) among the Desmi- 

 diacea. 



There hgis been much discussion of the question, whether the 

 Closteria are plants or animals, and as this inquiry is one of gen- 

 eral interest, the decision of which will affect the position of all 

 the family Bacillaria, I may be excused for giving at some 

 length, an account of the present state of the question. Eh- 

 renberg gives the following reasons for believing the Closte- 

 ria to be animals. 1. Their voluntary motion. 2. Their termi- 

 nal openings. 3. The incessantly moving organs placed against 

 the openings and sometimes projecting. 4. Their spontaneous 

 lateral division. 



Morren, in his celebrated memoir " Sur les Closteriees," (some 

 notice of which may be found in this Journal, Vol. xxxv, p. 122,) 

 supports the view that the Closteria are plants. 



Vol. xLi, No. 2.— July-Sept. 1841. 38 . ^ ,. „, 



