BY W. R. COLLEDGE. 173 



individuals, being adapted to the thickness of the matrix 

 of the colony. The extreme section of the tube is of stiffer 

 material, inflexible and adheres to the gelatinous matrix 

 with some degree of firmness ; but the rest of the foot and 

 body slides loosely within its own special cavity in the 

 colony. In contraction the lower portion especially- shrinks 

 into a close series of concentric folds. The principal body 

 muscles arise a short distance from the extreme end of the 

 tube to which they are affixed. They are six in number, 

 and proceed as separate strands upwards to near the anus, 

 where they divide into twelve branches, some of which are 

 inserted into the alimentary and rej^roductive glands, 

 while others pass on to the corona and are the means by 

 which it is invaginated. A number of glands are scattered 

 along the interior of the foot similar to the mucous glands 

 found in other rotifers of the same family. The mastax 

 is a large elongated organ, built on the melicertan tj^pe, 

 but differing from M. ringens and others in the details of 

 its structure. 



It lies across the centre of the face of the trochal disc 

 and is t^vice as long as it is high. It is hinged in the centre, 

 each side falling and rising about fifty times in a minute. 

 The central portion or incus of each jaw is broadly triangular, 

 and is destitute of the fine parallel teeth usually shown in 

 the jaws of Melicerta and Lacinularia. At each corner of 

 the base of the triangle is a blunt tooth, the sides are united 

 by a bifurcating rod. Three thin, wide arches form the 

 -exterior frame of each jaw. A rod from each arch passes 

 onward, and be'ow the incus is broadened into a spatu'ate 

 form, and lie with their flat sides parallel to each other 

 thus forming three large broad teeth at right angles to 

 the side of the incus. 



From the inner edge of the base of the incus, a rod 

 •extends to form the fulcrum, this instead of terminating 

 in a point as in M. ringens, broadens out into a wide base 

 for muscular attachment. The manubrium consists of 

 the three circular arches just mentioned. These are 

 strengthened by two rods and a transverse bar. They 

 -afford a wide attachment for the muscles, and furnish 

 £k strong leverage for them in the fulfilment of their work. 



