1882.] 



MICROSCOPICAL JOURNAL. 



103 



crop, are composed of two sharp, 

 slender hooks, with about four slen- 

 der, straight teeth at the inner base. 



The stomach is large, and the in- 

 testine very small and short, opening 

 on the ventral surface of the body 

 near the posterior end. 



C. bucinedax, sp. nov. The body is a 

 coriaceous, flattened sac, minutely 

 roughened over the whole surface, 

 nearly as broad as long, and about 

 three-fourths as thick. The dorsal out- 

 line is longest and strongly convex, 

 the ventral being usually somewhat 

 concave. The cup is oblique, the 

 ventral height being little more than 

 half the dorsal. Its lower wall usually 

 presents a shallow, longitudinal con- 

 cavity, so that the aperture is slightly 

 kidney-shaped. The surface of the 

 cup is more delicately roughened than 

 the body, and its edge is minutely 

 erose. 



In an average specimen the length 

 of the body, without the cup, was 

 o.i6-in., and its width 0.014-in. 



This rotifer has no means of at- 

 tracting its prey or bringing it within 

 reach, but depends wholly on such 

 animals as chance to swim into its 

 oval cup. When a stentor or other 

 animalcule of considerable size enters 

 the trap, the rotifer quickly puckers 

 up the aperture and contracts the 

 walls of the cup upon it, until it is 

 forced, with a sudden slip, into the 

 ample cavity of the pharynx. This 

 apparatus enables it to secure much 

 larger prey than the usual ciliated 

 structure ; but, in the absence of lo- 

 comotor organs, it can only live in 

 water swarming with suitable food. 

 In the aquarium mentioned it was 

 living almost wholly on the large 

 stentors. 



Measurement of the Power of 

 Oculars. 



Mr. W. H. Bulloch has devised a 

 simple apparatus for measuring the 

 magnifying power of oculars, which 

 is illustrated in fig. 33. It consists of 

 an ordinary microscope with an ob- 



