36 



INVF.UTEBKATE ANIMALS. 



tozoa than to tiny other. In these forms (fig. IG) the body is pro- 

 vided with long filamentous pseudojiodia, which stand out like rays, 

 and which may anastomose with one another. The body may be 

 quite soft, as in the common " Sun-animalcule " [Ai'tinojj/irt/s), but 



Fi^'. 10. — Jhteroplints spini/era, one of ttin HfJiozoa, greatly enlarged 

 (after Heitwig and Les?er). c c Contractile vesicles 



tliere ma}' lie, and often are, delicate sjiines of flint r.adiating from 

 the central s.ircodic mass, and there is sometimes a regular siliceous 

 skeleton. The Ileliozoa are further furnished witli the structures 

 which are known as the " C(jntractile vesicle " and " nucleus." 



