THE WHEEL ANIMALCULES 



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riding in clusters on the backs and sides of crustaceans. Among the Illoricata, 

 Balatro calvus remarkable for having no disc infests small water worms, to 

 which its clings by its enlarged foot processes; and Drilophagus bucephalus is 

 parasitic upon a water worm (Lumbriculus) , to which it clings, feeding by means 

 of its modified jaws. Other species again form internal parasites, the genus Albertia 

 being found in the interior of earth-worms, slugs, and annelids of the genus 

 Nais; while Notommata 

 may be seen swimming 

 freely within the spheres 

 of the beautiful Volvox. 



The members of the 

 order Bdelloidea swim by 

 means of their ciliary 

 wreath, and creep about 

 like a leech. The foot is 

 telescopically retractile, 

 and ends almost invari- 

 ably in three toes or 

 claspers. In this group 

 also the mode of life is 

 varied. Most species are 

 free living, but others at- 

 tach themselves to vari- 

 ous entomostracous crus- 

 taceans, and Callidina 

 parasitica is always found 

 clinging to the appen- 

 dages of the fresh-water 

 shrimp and the aquatic 

 wood louse. A special in- 

 terest attaches to this 

 group on account of their 

 vitality. If specimens be 

 inclosed in a cell con- 

 taining a little sand or 

 moss, the contents may be 

 dried over sulphuric acid 

 or heated up to 200 F., 

 or left to the neglected 

 dust of years, and some 



of the little creatures will revive if a drop or two of fresh water be added to the 

 sand. 



The order Rhizota takes its name from its members being fixed when adult, and 

 usually inhabiting a gelatinous tube. The foot is not retractile and ends in an ad- 

 hesive disc or cup. In the flower animalcules (Floscularia] , which may be found 



ANIMALCULE (magnified 200 times). 



