340 Illinois State Laboratory of Natural History. 



globular in shape and situated at the sides of the mastax. 

 Another pair, the so-called liver or gastric glands, more or less 

 kidney-shaped, are situated behind the mastax and on the 

 anterior part of the stomach, and, as their name implies, are 

 supposed to secrete a digestive fluid for the stomach. The 

 third pair are located in the foot, and are called the foot 

 glands. They are usually tubular, more or less elongate in 

 form, and secrete a sticky substance by means of which the 

 rotifer anchors itself to weeds, sticks, or other objects. 



No true circulatory or respiratory organs are present, 

 although there is an excretory system. This consists of 

 a pair of tubes or canals, one on each side of the body, 

 running almost its entire length, and connected posteriorly 

 with a contractile vesicle which, in turn, opens into the 

 cloaca. Upon each lateral canal are a number of small cup- 

 like structures, the vibratile tags, each one probably pro- 

 vided with cilia or Hagella by means of which the Huid of the 

 body is caused to tiow into these vibratile tags and thence 

 into the lateral canals, thence passing to the exterior by 

 way of the contractile vesicle and cloaca. While it is prob- 

 able that all rotifers are provided with a contractile vesicle, 

 this has not been demonstrated for every species. 



All rotifers, especially the more highly organized kinds, are 

 well provided with muscles for the extrusion and retraction 

 of head and foot, and for the working of the skipping ap- 

 pendages where such exist. These muscles are transversely 

 striated, and the stria' can be distinctly seen in such forms as 

 Triartlira, Polyarthra, and Pcdalion. 



A nervous system and various sense organs are also 

 present in rotifers. The sense organs consist of various 

 styles or seta; on the head and, usually, a brush of fine set» 

 on each side at the lumbar region. The brain is rather large 

 and is usually situated in front of and above the mastax. 

 From this brain nerve fibers extend to the various sense 

 organs. There are also from one to three so-called eyes, 

 which arc usually ruby-colored or black, and are situated 

 either on the posterior part of the brain or on the frontal 

 border of the head. They probably serve more for the 



