72 EVENINGS AT THE MICROSCOPE 



look through its tissues we shall easily find its ears, 

 though they are not quite so prominent as those of an ass. 



I subject the animal to a gentle pressure by means of 

 the compressorium, just sufficient to flatten its soft body 

 a little, without injuring it. And now, with this low 

 power, you may see what Siebold, a learned zoologist and 

 comparative anatomist, familiar with the curious phenom- 

 ena of life, truly calls "a wonderful spectacle." In the 

 neck of the little animal you discern, deep-seated in the 

 soft flesh, a pair of perfectly transparent globules, or blad- 

 ders, without any opening, but filled with a clear fluid, 

 in which there are some minute bodies performing the 

 most extraordinary evolutions. They constantly keep up 

 a series of swinging or balancing movements, sometimes 

 rotating, sometimes forcibly driven in a certain direction, 

 then in the opposite, yet no single one ever by any acci- 

 dent touching the walls of the capsule in which they are 

 contained. If the capsule be ruptured, the motions in- 

 stantly cease. These little bodies are of a calcareous 

 nature; and they are called otolithes, that is, ear-stones. 

 The most that we know of these curious capsules, which 

 are indubitably ascertained to be organs of hearing, we 

 owe to the observations of the eminent zoologist just 

 named, and you may perhaps like to know a little more 

 about them. 



Siebold says that a concentric depression is evident in 

 these otolithes, and that there may be seen in the centre 

 of the greater number of them a shaded spot, or rather a 

 minute aperture, which penetrates through the concretion 

 from the one flattened surface to the other. Subjected to 

 a strong pressure, the otolithes crack in radiating lines, 

 separating often into four pyramidal pieces. This separa- 



