THE WHEEL ANIMALCULES (ROTATORIA) 563 



two glands lying in the foot (Figs. 856 and 857, mg); these secrete 

 a sticky, tenacious mucus, which may be discharged either at the 

 tip of the toes, or at their base, so as to flow out over their surface. 

 By this mucus the rotifer may attach itself loosely to objects of 

 various sorts, so that the movements of its cilia may continue to 

 bring food to the mouth without carrying the rotifer away from 

 its anchorage. Often the mucus is drawn out to form a long 

 thread, like that produced by a spider; from this thread the rotifer 

 remains as it were suspended, swinging about from side to side at 

 a distance from the point of attachment, but not breaking away 

 from it completely. At times the rotifer spins out behind it a 

 thread of mucus as it progresses slowly through the water; this 

 thread steadies its course and keeps it connected with its point of 

 departure. The foot and toes are modified in many ways in other 

 groups, as will be seen later. 



For controlling motion the rotifer has a nervous system and a 

 number of sense organs. The chief part of the nervous system is a 

 large ganglion known as the brain (br), lying on the dorsal side, 

 just above the mastax, at the anterior end. From the brain 

 nerves pass in many directions to the various organs of the body. 



Several different kinds of sense organs are found in the rotifers. 

 In some part of the anterior end, usually attached to the brain, 

 there are usually one or two red pigment spots; these are supposed 

 to be organs of light perception, and are known as eye-spots (e). 

 In a few cases three or more of these are found. Sometimes the eye- 

 spots are not attached directly to the brain, but are connected with 

 it by nerves (for example, in the genus Rotifer). The eye-spots 

 sometimes bear on their anterior surfaces hemispherical crystalline 

 lenses. In some rotifers eye-spots are lacking. 



Many rotifers bear sense organs of various kinds on the corona 

 (see for example the corona of Synchaeta, Fig. 883, or of Hydatina, 

 Fig. 906, B). Such sense organs are less common in the Notomma- 

 tidae than in more specialized rotifers. 



Almost all rotifers have a pair of sense organs on the sides of 

 the body behind the middle; these are known as the lateral an- 

 tennae (Fig. 857, C, la). Either another antenna, or a pair of them, 

 is found on the dorsal surface of the head, just above the brain; 

 these are known as the dorsal antennae (Figs. 856 and 857, da). 



