SOME AQUATIC WORMS, ETC. 199 



body bearing numerous fine, short hairs. Two dark or 

 black eye-spots are generally present, one on each side 

 in advance of the mouth. The blood is red. Many 

 narrow, colorless tubes, with a ciliated lining, 

 are to be noticed on both sides of the intes- 

 tine. They are much looped and twisted, and 

 are supposed to play some part in respiration, 

 or to represent the kidneys of animals higher 

 in the scale. They are bathed in the color- 

 less fluid filling the cavity of the body, and 

 change their position rapidly as this fluid 

 flows to and fro, following the movements of the worm. 

 Ndis is the commonest of the aquatic worms, being 

 very frequently found among Algae in shallow water, or 

 on the leaflets of various plants, especially, according to 

 the writer's experience, in Sphagnum, in company with 

 Pristina and Chaetogaster. 



Dr. Joseph Leidy ? s papers, published in the Journal 

 of the Academy of Natural Sciences, Philadelphia, and 

 elsewhere, are the only ones to which the student can 

 be referred for further information in connection with 

 the aquatic bristle -bearing worms, as Dr. Leidy is the 

 only naturalist who has seriously studied the American 

 forms and published the results of his work. 



