SCOLECIDA. 127 
consequence of their great similarity in external appearance. 
They are, however, of an obviously much higher grade of struc- 
ture. One of the most remarkable phenomena presented by the 
Rottfera is found in the undoubted fact that in spite of their 
complex organisation and aquatic habits they can be dried, and 
again brought to life by the addition of a little water, and that 
this desiccation and restoration to life can be apparently repeated 
many times in succession without injury. 
TABULAR VIEW OF THE DIVISIONS OF THE ANNULOIDA. 
Ciass I. ECHINODERMATA, — Integument more or less highly 
charged with lime, or leathery. A water-vascular system, which 
usually assists in locomotion, and usually communicates with the ex- 
terior. Adult more or less distinctly radiate. 
Order 1. Crinoidea.—Ex, Feather-star (Comatula). 
Order 2, Blastoidea (extinct). 
Order 3. Cystoidea (extinct). 
Order 4. Ophiuroidea.— Ex. Brittle-stars and Sand-stars. 
Order 5. Asteroidea.—Star-fishes. 
Order 6. Echinoidea.— Ex. Sea-urchins. 
- Order 7. Holothuroidea.—Ex. Sea-cucumbers. 
Crass II. ScoLEcrpA, — Usually flattened or cylindrical ; soft- 
bodied ; water-vascular system not assisting in locomotion ; no proper 
blood-vascular system; nervous system not disposed in a radiating 
manner. 
Order 1. ZYentada.—Ex. Tape-worms. 
Order 2. Zrematoda,—Ex. Flukes, 
Order 3. Zurbellaria.—Ex. Planarians. 
Order 4. Acanthocephala.—Ex. Echinorhynchus, 
Order 5. Gordiacea.—Ex. Hair-worms. 
Order 6, Mematoda,—Ex. Round-worms. 
Order 7. Rotifera.—Wheel-animalcules, 
