POL YCISTINAPOL YZOA. 1 5 5 



soda and a similar weight of water for one hour. After 

 allowing to settle, the " flock " must be poured off and the 

 boiling with soda repeated, with intermediate washing 

 several times. Rhopalocanium ornatitm, Podocyrtis Schom- 

 burghii, and Astromma Aristotelis are, perhaps, the most 

 beautiful of this class. 



Books which may be consiilted : Haeckel's ' Die Radio- 

 larien ' ; ' The Micrographic Dictionary.' 



POLYZOA. These interesting objects have, by the 

 researches of modern inquirers, become much more known ; 

 they are both marine and fresh-water, and may be found in 

 many rivers and canals. 



On the sea-shore they are very plentiful, forming a crust 

 on submerged rocks, or attached to stones, shells, and sea- 

 weed. The individual animal is termed zpolypide, and the 

 colony a ccencecittm, which latter consists of an aggregation 

 of cells or cups, often taking elegant and vegetable forms. 

 Most Polyzoa are fixed organisms, but one at least the 

 Cristatella mucedo is capable of locomotion. 



One beautiful form, the Lophopus crystallinus, may be 

 found constantly in the Gorton Canal, near Manchester, 

 and is much sought after by microscopists, visitors to the 

 neighbourhood ; it is shown in Fig. 142. 



The study of these animals is an interesting one. In 

 L. crystallinus, as shown in the figure, a is the region of the 

 mouth ; , the oesophagus ; c y the stomach ; d, the intestine ; 

 e are the retractory muscles ; /, a statoblast ; h, the mouth ; 

 i, tentacles retracted, partly within cell ; k, the outer trans- 

 parent envelope ; /, the perigastric space ; m, the lopho- 

 phore ; and at n the tentacles have been excised, to show 

 mouth. 



Of marine Polyzoa, the sea-mat, or Flustra foliacea, may 

 be taken as a type ; it is most plant-like and flexible. The 

 cells are narrow at the base and rounded at the end, with 



