Spoon-worms and Lecclies. 



67 



but which remain permanently in this ciliated condition. 

 In these the ciliary lobes are prominent and rounded, 

 acting as locomotory organs, and from the rapid vibra- 

 tion of the cilia which clothe them they FlG - 39- 

 seem like rotating wheels, hence these 

 little creatures are called Rotatoria. They 

 are microscopic in size, varying from 7 ^th 

 to \\\\ of an inch in length, but from the 

 exquisite transparency of their bodies the 

 details of their organisation can be seen 

 by the aid of the microscope. The male 

 rotifers are few and small and have no 

 digestive canal ; the females have a com- 

 plex nutritive system, and many species 

 are provided with an organ of mastication 

 like an anvil acted on by two hammers. 

 These animals can bear much ill usage, 

 and are capable of reviving again on being 

 moistened, after having been almost com- 

 pletely dried up. 



On irritation the trochal disks (fig. 

 39, c) can be retracted into the cavity of 

 the body, from which they are gradually 



* Rotifer vulgar- 



protruded again on the cessation of the is. a, mouth- 

 lobe ; b, eye- 

 ochal 



stimulus. Some rotifers are rooted ; 

 others possess a forceps posteriorly, 

 whereby they can hold on to foreign 

 bodies ; others again are contained in a 

 vase-like sheath, into which they can re- 

 tract themselves, on being irritated. 



CLASS VI. Spoon-worms or Squirt- worms, 

 Gephyrea, These are interesting marine worms whose 



spots ;c, troch 

 disks ; d, chew- 

 ing organ with 

 calcar in front; 

 , malleus ; f, 

 alimentary ca- 

 nal ; g, gastric 

 caeca ; k, de- 

 veloping em- 

 bryos ; /, anus. 



