258 EVENINGS AT THE MICROSCOPE 



sides and narrowing a little at the mouth, has one side 

 of its rim furnished with four spines, the middle pair of 

 which are very slender, sharp, and needle-like; the other 

 side of the rim is undulated, but not toothed. The bottom 

 of the cup terminates in two broad blunted points when 

 seen directly in front; but a lateral view considerably 

 modifies the whole form. Then you see that the back of 

 the cup is much more swollen, the belly-edge being nearly 

 straight, and that this latter descends much lower than 

 the dorsal line, the bottom being as it were cut away 

 obliquely and slightly hollowed. Between the two bot- 

 tom points, there is a round opening, for an object which 

 we shall see presently. Such is the shell, or lorica, as it 

 is technically called, which is of a rather stiff, elastic con- 

 sistence, of a horny (chitinous) texture, and of the most 

 glassy transparency, permitting us to trace every vessel, 

 every organ, and every function of the animal within the 

 shell with perfect distinctness. The little creature is of 

 unwonted dimensions in its class, for it is one thirty-sixth 

 of an inch in length. Hence it is just visible as a white 

 speck moving in the water, to the unassisted eye, while a 

 pocket lens reveals its beautiful form. 



Within this translucent shell you see a confused mass 

 of moving viscera, a multitude of irregular sacs and bands, 

 lying over each other, whose crowding, changing, and 

 vanishing lines distract the attention, and prevent you 

 from making out anything definitely. But a waved out- 

 line of hyaline flesh is protruding from the rim of the 

 shell, and now, having reached beyond the level of the 

 spine-points, it rapidly unfolds into three broad flattish 

 lobes, and in an instant each of the two lateral ones is 

 crowned by a wheel of dark points in rapid horizontal 



