170 MICROSCOPY FOR BEGINNERS. 



often be seen in the animal while still in the egg, for 

 even there, when almost ready to escape, it is also very 

 restless. The eggs are often found on the slide, with 

 the young Chsetonotus doubled up within. 



The eggs by which Chsetonotus is reproduced are 

 formed in an ovary placed in the median line of the 

 body immediately above the intestine. Usually only 

 one egg is formed at a time, but it is not rare to see two 

 or more in various stages of ovarian development. Upon 

 the absence or presence of an egg in the ovary depends, 

 to a great extent, the degree of convexity of the back. 

 The eggs are dropped anywhere in the water, and left 

 to the care of nature. 



The food consists of the minute particles of decayed 

 animal and vegetable matters so abundant in the soft 

 surface of the mud at the bottom of our shallow ponds. 

 These particles are taken in with a peculiar and a sud- 

 den snapping movement of the cavity of the oesophagus, 

 easily to be seen but difficult to describe. Diatoms are 

 rarely swallowed. 



So far as their classification is concerned, these attract- 

 ive little animals have given naturalists a good deal of 

 trouble. Some have said that they belong with the 

 Rotifers ; others have placed them among the Infuso- 

 ria ; others have called them low worms, putting them 

 among the Turbellaria ; and still others think, and they 

 are doubtless correct, that Chsetonotus should stand in a 

 group by itself, among the worms, and not very far from 

 the Rotifers. 



