88 One TJwusand Objects 



684. HAIRY ALCYONIDIUM (Alcyonidium hirsutwri). 

 Equally common on seaweeds at low-water mark. Sur- 

 face covered with little conical teats or papillae, from each 

 of which emerges a polyp-head, furnished with sixteen 

 tentacles. 



685. GREEN HYDRA (Hydra viridis). Very common 

 in ditches, attached to duckweed. Green, just visible to 

 the naked eye, like buds ; body nearly cylindrical, ending 

 in from six to ten tentacles, each scarcely the length of 

 the body. (PI. XI., fig. 20.) 



686. BROWN HYDRA (Hydra fused). Not common, 

 under similar conditions. Brownish, with from six to 

 eight arms, which are capable of being extended to a 

 great length. (PI. XL, fig. 13.) 



687. ORANGE HYDRA (Hydra vulgaris). In weedy 

 ponds. About the same size as the Green Hydra ; of an 

 orange or orange-brown colour. Tentacles seven or 

 eight, sometimes more, longer than the body 



PALATES or Tongues of Molluscs afford a great variety 

 of objects. They are sometimes mounted dry, and some- 

 times in balsam. 



688. PALATE OF DOG-WHELK (Purpura lapillus). In 

 three series ; the central simple and broad, the side teeth 

 flat. The palates are easily obtained from these common 

 molluscs, and are favourite objects. 



689. PALATE OF WHELK (Bucrinum uttdatum). The 

 central band consists of equal rows of straight teeth, 

 seven in a row. The outer band on either side V-shaped, 

 with three inner and one outer curved teeth. 



690. PALATE OF LIMPET (Patella vulgata). Central 

 teeth in fours, alternating with inner lateral teeth in pairs. 

 The outer teeth on each side in threes. 



691. PALATE OF PERIWINKLE (Littorina litored), 

 Narrower and simpler than in Cydostoma elegans, 



692. PALATE OF NERITINE (Neritinafluviatilis). Teeth 

 in several series : central minute, inner lateral large ; the 

 outer lateral teeth uniform and very numerous. 



693. PALATE OF CYCLOSTOMA (Cyslostoma elegans). 

 With seven series of teeth : the central recurved at the 



