PROTOPHYLES. 35 



length of this specimen was found to be the one hundred and forty-fourth part of 

 an inch. This species varies in size, however, from one-one hundredth to one-two 

 hundred and tenth of an inch. 



THE SWOLLEN EUNOTIA. In figure 34 is shown the shell of a species of diato- 

 maceas which differs a very little in its characteristics from those just described. 



Fig. 34. 



Fig. 35. 



It is called the Swollen Eunotia. The shells vary in length from one-eleven hun- 

 dred and fiftieth of an inch to one-two hundred and fortieth, and are of the shape 

 represented in the figure, which exhibits a side view. A furrow (a, a) runs the 

 whole length of the shell, along the middle of each side, and from this furrow 

 numerous curved ribs branch out towards either edge. The furrows are plainly 



discerned in the shell ; but are detected with difficulty in the living organism, 

 on account of the color of the body. So closely are the ribs placed together 

 that no less than eight are contained within the space of one-twelve hundredth 

 of an inch. Figure 35 is the representation, of several living individuals of this 

 species, found upon a branch of conferva, which is the bright green vegetable 

 matter that floats upon stagnant waters during the spring and summer. The 

 Eunotia multiplies by self-division, and in figure 36 an individual is exhibited 

 undergoing this process. The separation is seen to take place in the direction 

 of the length, and in each half we can discern another line of division (a, a; &, 5) 

 just commencing. Through this line, when the divided portions have arrived at 

 maturity, and each has become a perfectly developed plantule, another separation 

 occurs, and thus proceeds interminably. 



