204 Transactions of the 



suddenly empties in twenty seconds, or less; -while the oldest 

 inhabitant of my oldest tank had a pulse calmly beating one in five 

 minutes. 



With difficulty, but certainty, five pairs of " vibratile tags " 

 may be traced in a selected victim, by crushing (or otherwise per- 

 suading it to be quiet), and seeking the flicker before the creature 

 dies. A tag may be seen on each side beneath the base of the 

 serrated processes, or a little lower, and so on downwards, four 

 more at about equal distances approaching the contractile vesicle ; 

 but I fail to detect any tube connecting the tags with each other, 

 or with the vesicle. On either side of the abdomen is seen a group 

 of rudimentary ova, or a single large granular egg. 



C. vaga bears on its back an antenna a little broader laterally, 

 and shorter than common (shown in Figs. 2 and 3), and at the 

 extremity of its foot-tale three soft toes ; mounted on the next 

 joint above are the usual two spurs or horns. These, I find, act as 

 supplementary toes in this species, and in P. roseola : — whenever an 

 extra firm hold is required, the penultimate false joint is carried 

 down, and the spurs, as well as the small toes, are brought into 

 adhesive contact at the anchorage ; assisted, no doubt, by the viscid 

 fluid which all rotifers appear to secrete more or less abundantly 

 (vide foot-tail, Fig. 3). 



As to the mastax of any philodine, it would be discreet in me 

 only to refer to Mr. Gosse's memoir in the ' Philosophical Trans- 

 actions ' ; * but the worst part of valour urges me to make a few 

 remarks on the most simple part of a difficult subject. 



If C. vaga be killed by boiling, poisoning, or unduly roasting ; 

 the body, left in a tank and not compressed, will slowly rot away, 

 and leave all the hard parts of the mastax clearly displayed, gene- 

 rally adhering undistorted and in natural positions. As an ex- 

 ample, take one of these (Fig. 6 a) : two transparent plates curved 

 like watch-glasses, convex side outward, each having two thickened 

 lines or teeth to lock into each other, and from thirty to forty fine 

 teeth, all in the one-thousandth part of an inch; on focussing 

 through the faces of these striated plates (just on the right and left 

 of the straight edges where they are in contact), we see a pair of - 

 rami, the strongest and thickest hard part of the entire rotifer. 

 The rami have two notches on the parts corresponding to the 

 coarse teeth of the plates described, and on the side opposite to the 

 notches each ramus has a short branch (Fig. 5). Take another 

 example: In this the straight edges of the curved plates are 

 forced apart, only being kept together by the hinge at the top ; 

 while the inner rami will be seen to have turned on their long axes, 

 bringing their short branches into sight (Fig. 7 a). Many self- 



* " On the Manducatory Organs in the class Botifera," by P. H. Gosse, Esq., 

 1 Phil. Trans.,' Feb. and March, 1855. 



