INFUSORIAL ANIMALCULES. 



are they, that fifteen are contained within Fi =- 34< 



every twelve hundredth of an inch in length. 

 A side view of the same animalcule is 

 shown in Figure 3 4, exhibiting the currents 

 produced by its motion through the water. 

 This species of Navicula varies in size from one-seventieth to one-one hundred and 

 fifteenth part of an inch in length. 



GOLDEN NAVICULA. Figures 35 and 36 are representations of a beautiful 

 species of the golden Navicula, so called, because Fig. 35. 



the clusters of eggs within the shell are of a 

 bright yellow color. They are seen in the engra- 

 ving occupying the central portions of the shell, 

 and filling up its numerous flutings. The shell is 

 of an oblong oval shape, and possesses the utmost 

 regularity in its structure. In figure 35, the ani- 

 malcule is seen from above ; in Figure 36, a side 

 view of the same creature is presented : by com- 

 paring the two drawings, it is seen that the shell 

 tapers more in the latter case than in the former. 

 The above figures are faithful delineations of a living golden Navicula, obtained 

 by Dr. Man tell : the 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 37 is shown the shell of a species of ani- 



Fig. 37. 



Fig. 36. 



Fig. 38. 



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

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

 hundred 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 fur- 



