Sketch of the Infusoria of the family Badllaria. 293 



This is a very beautiful genus, its species presenting elegant 

 star-like arrangements of green corpuscles, some of which closely 

 resemble in form the stars and badges of honor worn in Europe. 



There appears to me to be much confusion in the specific char- 

 acters, arising from the circumstance, that the number of corpus- 

 cles in the different rows has been made a character of specific 

 importance. From what I have seen of the species, 1 am satis- 

 fied that the number of corpuscles in a star is liable to great va- 

 riation in the same species. Perhaps the form of the corpuscles 

 would prove a more certain character. 



1. Micrasterias Tetras. (Fig. 19, PI. 1.) Four corpuscles united 

 in form of star, the edge slightly notched. 



This is a very minute species, which occurs in ponds near West 

 Point. I have also noticed it in Virginia. 



2. Micrasterias Boryana. (Fig. 20, PI. 1.) Ten corpuscles in the 

 exterior circle, five in the interior, and one in the centre, edge acutely 

 dentate. Corpuscles ^V to yj^ of line. 



It happens accidentally that our figure represents an individual 

 having just the number of corpuscles above described. I am 

 satisfied, however, from frequent observation, that the same spe- 

 cies sometimes has a much greater number of corpuscles, certainly 

 another roio of fifteen is often developed. It then agrees with 

 M. tricyclia of Ehrenberg. It is a very beautiful object for the 

 microscope. I have found it in New York, Virginia, and in Ouis- 

 consin. 



3. Micrasterias . (Fig. 21, PI. 1.) Corpuscles very nume- 

 rous, forming large imperforate plates of a circular or elliptical form. 

 Exterior corpuscles deeply emarginate, each having two projecting 

 points. 



This large and very beautiful species is not uncommon in ponds 

 near West Point. 



EUASTRUM. 



Free, carapace simple, imivalve, compressed, binary, sometimes 

 quaternary, having the form of a two-lobed disc or lamina, often 

 dentate. 



The elegant forms and emerald green color of the species of 

 this genus render them exceedingly fine objects for the micro- 

 scope. The forms, as usually seen, appear tabular, but when 

 thrown on their sides by means of a compressor, they show con- 

 siderable thickness. 



