OF THE FAMILY BACILLARIA. 127 



rent 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 

 Desmidiacea. 



There has 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 maybe excused for giving at some length, 

 an account of the present state of the question. Ehrenberg gives 

 the following reasons for believing the Closteria to be animals. 

 1. Their voluntary motion. 2. Their terminal 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 Clostcriees^'' (some 

 notice of which may be found in Silliman's Journal, Vol. xxxv. 

 p. 122,) supports the view that the Closteria are plants. 



Meyen, in his report on Vegetable Physiology, for 1837, 

 (p. 54, Francis' translation,) and also in his Pflanzen Physiolo- 

 gie, Vol. III. p. 437, has brought forward the fact of the presence 

 of starch, in the Closteria, as conclusive evidence of their being 

 plants. He states that the large and small globules in these bod- 

 ies " at certain times, and particularly in spring, are almost wholly 

 composed of starch." He adds that in the month of May he had 

 observed " many specimens of Closterium, in which the whole 

 interior substance was granulated, and all the grains gave with 

 iodine a beautiful blue color, as is the case with starch, which is 

 not an animal product." 



In the Annals of Natural History for August, 1840, (No. 33, 

 p. 415,) is given a notice of a paper read by Mr. Dalrymple be- 

 fore the Microscopical Society of London. As this paper gives 

 a good idea of the present state of the discussion concerning the 

 nature of the Closteria, I believe that no apology is necessary for 

 taking from it the following extract, especially as my own obser- 



