WHEEL ANIMALCULES 



163 



w.a 



side (l.l. 1 and /./. 2 ), of which that on the right side only 

 is seen, end in beautiful fringed hairs, which are only 

 seen elsewhere in the Crustacea (water-fleas and others). 

 Those on the lateral limbs and 

 the great ventral limb (Fig. 36) 

 are set in two groups of four on 

 each side of the free end of the 

 limb, whilst those on the dorsal 

 leg (d.L) are apparently not so 

 numerous. I have corrected the 

 drawings, Figs. 35 and 36, by re- 

 ference to actual specimens kindly 

 given to me by Mr. Rousselet. 



The 500 different species of 

 Wheel Animalcules or Rotifera 

 differ from one another in the ex- 

 act shape of the wheel-apparatus, 

 in the jointing of the body and its 



general shape, and in the develop- F[G ^ Rotifer 



ment, in some, of a hard skin or 

 shell like a turtle's or tortoise's shell 

 (Fig. 37) over that broadest region 

 of the body in which in our Fig. 34, A, 

 the stomach marked "St" is placed. 

 They differ also in the shape of the 

 gizzard's teeth, in the presence of 

 paddles or legs (in Pedalion alone), 

 and in the presence in some of longer 

 or shorter projecting movable rods 

 or bristles in pairs or in bunches. 

 Many build for themselves tubular 

 habitations of jelly or of hard cemented particles. They 

 are all minute (from the i-i2th to the 1-500 in. in length). 

 They are divided into five principal groups, which are 

 (i) the crawlers, like the common Rotifer (Fig. 34), which 



Noteus quadricornis to 

 show its curious four- 

 horned carapace from 

 which the wheel apparatus, 

 wa, emerges in front, and 

 the tail, ^, behind ; some- 

 what as the head and tail 

 of a tortoise emerge from 

 its protective ' ' box " or 

 carapace. The ridges on 

 the horney covering of the 

 Rotifer recall the horney 

 plates of the tortoises and 

 turtles. 



